If you're that concerned with the life of the engine, a rotary is not for you. These cars are not designed for daily driving and reliability, but rather it's a purpose built sports car.

Most people get a long life out of their engine. Others blow them right away. It all comes down to your mods, tuning, and how well the person built the motor (unless it's a mazda original). If you "UP DA BOOST" without adding sufficient fuel, you will blow your motor. This is true for most piston engines as well. Rotaries are just incredibly sensitive to pre-detonation, or knock. I have 5,000 miles on my reman, with full intakes, exhaust, massive front mount intercooler, a few reliability mods, powerFC, and 12.5psi. No issues. I am picking up a wideband controller and EGT gauge shortly to keep my AFR and timing in check.