I don't know if this is still the case today, but about 10-12 years ago, it was the 'common wisdom' that aluminum frames were not meant for extended use, but rather to be raced a season or two and then retired, because the metal would fatigue and the frame would not be safe.

This might have simply been a bit of retro-grouch lore, or perhaps back then aluminum frame technology was less refined and frames _were_ weaker.

Looking at the godzilla tubing and giant gussets on Al frames today, i doubt this is still the case, unless you are jumping off small buildings on a daily basis.