Of course the problem with many discharge fixtures is duty cycle and warm up time. So that has to be kept in mind when using them.
Yep, you definitely need to keep this in mind, though usually with discharge fixtures you just turn them on at the beginning of use and leave them on until you're done. The units will have a shutter so that you can essentially turn them off without dousing the lamp. The Tempest Series is a bit of an exception to this, but it's also a very specialized fixture.
The Snipers (both the 2R and the Pro models) have only been discontinued for a little over a year so they can still be found every once in a while. The Ninja is in the same boat too. One thing to note about these fixtures is that they're "beamy", in the sense that you really need fog or haze to get the full effect. The Ninja puts out enough beams to look okay without fog, but prisms aside the Snipers are single-beam units and won't be effective without some sort of atmosphere enhancement.
If you'd rather not use fog or haze I'd look in the direction of Martin Wizards. There have been many incarnations of this effect over the past decade (the Rush Wizard and ADJ Warlock being the most recent), but these units put out a massive number of beams with around 180 degrees of coverage, so they'll look good with or without fog. I still use my Martin Mania EFX600 version of the effect (150w discharge) and they're still going strong a decade later.
If you must buy new and don't want to stalk ebay for months many of the direct-from-China vendors such as Artfox still sell the off-brand variants of the Sniper, Ninja, and Wizard/Warlock. Pros and cons to that route as well, but just throwing it out there. Glad this helps and best of luck with the project!