I'm with bitsnake on this one. The 154 is a good trans, and can hold the power, but the DRIVER has more to do with long life than the transmission. (All things being equal.)
Correct rebuild and some coatings, or custom parts or some from Marlincrawler are not a bad idea. My 154 was rebuilt, and I just deburred and coated a stock new first gear thrust washer, so far, no problems.
Replaced the worn shift forks, and coated the wear surfaces etc. Also pressed the tailhousing bushing out and coated it with moly. (I did not like the tolerance there, and the coatings brought everything into the "tight" range, almost too tight according to the guy who did the work.)
I also agree with the clutch note. If you run a unsprung clutch, your going to F'up your transmisison in short order. If you powershift all the time, your going to break transmissions too.
Rebuild your trans right, and run a quality synthetic gear oil in there, and you should be fine if you don't drive it like you stole it.