They'll be fairly reliable as long as you keep the maintenance on time, make sure you keep it filled with oil, make some reliability-related mods, and don't make many high-power mods or beat the piss out of it.

But it won't last forever, you'll have to replace it at some point.

This is on the 3rd gens, at least. If you want a truly reliable rotary, get one that's isn't turbo'd.