A naturally asparated wankle rotary engine is very reliable. It will last as long if it is not beaten or improperly maintaned. The RX-7 turbo and before that the Cosmo gave the wankle a very bad name in thier poor reliability. With the Turbo heating the engine higher then the apex seal would allow, and cause them to wear very quickly. Mazda has made many advances on the oil injection of there design, and are working on a supercharging system to get more power out of the engine. The inlet port and exhuast port were moved to the side casing of the housing to reduce apex seal wear, and increase longevity.
Info on the Rotary engine
Also, I just want to clearify that I was not implying that this was the BEST engine at anything, other then being relativly efficient. with only 3 moving parts, and no loss of energy in taking linear motion and turning it into rotating motion.