No, I don't mean how long it will continue to work - goodness, if you treat a flash right you can get decades out of it. Exercise it regularly and don't drop it off a cliff...
I mean... how does the performance of the new Fujifilm EF X-500 stack up in a working situation - where you have to use it to satisfy the client...rather than your desire to fiddle with new gear. Let's go out on different jobs:
1. The Event.
The party, ball, graduation, awards ceremony, etc. The grip and grin, speeches at 8:00, 2000-shot corporate gig where you stay sober and everyone else doesn't. The you-get-paid-if-anyone-buys-a-picture job.
Well, you are going to need to shoot those 2000 shots consistently - well-exposed if you can, but at least all the same. The last thing in the world that you want to do is sit there pushing sliders on a computer later. If they are going to be similar poses and groups you can probably trust the TTL to give you a good run off the faces and clothing - formal males suits are going to have similar reflectance and even the ball gowns tend to be alike. If you are going to do the Mardi Gras resign yourself to having the exposure system overwhelmed every now and then.
The TTL can be skewed, however, if needed...say a situation with high-reflectance stage costumes in a great many of the shots. Dive into the page button and then the +/_ exposure compensation button. twist the control wheel for up to 5 stops plus or minus output. This is vastly better than the Fujifilm EF-42 flash that only allowed + or - 1.5 stops. The fact that the X-500 does in in one dial turn vs the the 8 button presses and 20 seconds waiting time of the older flash is really significant.
Likewise the recycling time - I count 2.5 seconds on fresh batteries from a full manual dump to recharged. The EF-42 could barely manage in 6-8 seconds. Some events are very much run and gun and if your flash is not ready almost instantly for a follow-up shot, you either have to talk like a parrot to keep the subjects still for that 8 seconds or lose them entirely.
2. The Wedding.
This is like a corporate event but with a CEO in a white dress ready to explode if anything goes awry. You can multiply the pressure as much as you like - pressure to shoot far too many pictures, to be everywhere at the same time, and to do things as fast as possible. Plus the pressure to have multiple sets of equipment ready to go at a moment's notice. In that respect the new flash is a bit more expensive than the old one, but weddings are not the time to skimp.
Will you get a chance to use the multiple flash capability of the X-500? You have three groups at your disposal from the main X-500 control panel - they can be manual, TTL, or a percentage TTL that you can alter as you go on. The big group, the bridal waltz, the speeches, the formals - they all lend themselves to the studio-lighting approach of multiple groups.
As a wedding pro you will have also worked out how flash modifiers and stands can be used in these situations. You do get a flash foot with the EF X-500, of course, but you need to match it to some suitable stands. You also need an assistant, but then you knew that after your first wedding...
3. The Grande Portraite.
Funny how the mighty all want to look good, but grant portrait photographers tiny little windows of opportunity to actually do the job...Time is money is power is prestige...
Well, if you are going to play their game, play it fast. Main and fill and as many flattering shots as you can suggest in your 15 minutes with His Moneyship or Her Publicityship. The Mag Mod flash attachments may well help, as will the facility for multiple groups of lights. The fact that these are speed-lights with no extra battery packs is a blessing - less to haul in and out. The rapidity of recharge and of control changes is also vital when you are dealing with people who have decided that they have so much money and power that they need not be patient...
4. The School/ Santa/ Sports Carnival Portraits.
These are easy - just work out your main/fill multiple group setup in advance, sandbag the stands down, and take your medication. It will all be over in 6-8 hours. The fact that you can expect about 600 full-bore TTL shots out of a set of lithium batteries us a good thing - it will go down to about 150 with regular alkalines. If you plan to do your Santa photos from an armoured emplacement you may be able to arrange for a 6V power feed and the auxiliary plug of the Ef X-500 will allow you to shoot an unlimited number.
Note: there is a thermal protection circuit in the Ef X-500 that will shut it down if you have been shooting far too much far too fast. It will come on again when the temperature goes down.
5. The Advertising Business.
Well, as the sky is the limit for ideas, ( but rarely paid at stratospheric prices...), you can use a brace of EF X-500's for a lot of stuff. They have the sort of manual power control that dials down to 1/512th of full power, so that they can be used for tiny little multiple flashes. If your camera will do it, you can shoot multiple shots in a fraction of a second for stroboscopic effects. You can stop peak action at high shutter speeds - again if you are using the X-T2 or X-Pro2.
On a good day you can get a picture at 1/4000 of a second and capture a frame of art directors midway between changing their minds.
6. The Science Lab.
Here's where those tiny slices of light are the most use - scientists are always trying to take pictures of little specimens or delicate surfaces that wash out under stronger light. Three of them with TTL/ group are controllable and precise and a lot less of an impost on the department's budget than trying to do the same thing with studio flashes or portable battery and head kits.
Field workers can break these a lot less than they could a suitcase full of heads and batteries. And electricity in the sticks is more likely to be available in AA form than mains power.
7. The Real Estate Business
Hello 3:00 AM again...well, if you need to light up an interior there is nothing better than three speed lights and some Mag Mod Domes. The EF X-500 so equipped and hidden round corners and behind furniture is the answer for making pokey dark interiors look livable. You can group control them to balance the result and you can put dedicated gels into the mag Mod holders to try to match whatever the dawn or dusk is trying to do.
Try everything. If the images don't work there is always tomorrow and the owner of the place won't mind keeping everything off the tabletops for another day...