NP231 rear oil seal life span?

What can I expect for the life span of this seal? I had read they are prone to fail do to design. I just got the new one and curious if these go out every couple of months or years. I'm pretty sure this one went bad due to me playin in the mud for 2 days ( hey we only get mud like 2x a year here in Phoenix !!) But I read goin offroad will speed up the seals life span also.

There are alot of factors that effect seal life. The most significant is temperature fluctuations. If the seals change temperature rapidly it is very hard on them. Vibrations can shorten the life of seals also. Cleaning the undercarriage after being in the mud will help also.