If your only concern is durability/reliability, and you do not need a high-voltage mod, then the Provari obviously fills the bill as one of the most durable mods out there.
If you are looking for higher voltage, or a mod with more advanced features then you may want to look elsewhere. No knock at all on the Provari, but personally, I change tanks frequently and prefer a device that has vw...but as long as the features of the Provari meet your needs, it is hard to impossible to find the combination of very rugged build combined with a warranty that is actually worth something.
Safe to say that you will not end up with a collection of Provari paper-weights.