heh... just take care of them.. All 3rd generation RX-7's are Twin Turbo'ed factory. If you see single turbo's, those are aftermarkets for bigger power. People who blow their seals are people who are ignorant in maintaining their FD's. They probably ignore the engine knocks or even let it over heat. For me, i did the reliability mods such as a new radiator, DP, interncooler, silicone vacuum lines, and ported the engine. (mild street port). I also had the car tuned for a little power, but with safety in mind.
remember, there are still Turbo 2's out there that has over 170k on the ORIGINAL engine out there. But of course, if i go 3 or 4 rotor, it's gonna probably be naturally aspirated, or a turbo with modest boost (8psi as opposed to my current 12psi)