From another perspective let's keep in mind that Tomlinson has 2,044 touches in five years in the NFL. That's 400+ touches per season. Shaun Alexander is also in this elite category not just in terms of fantasy value, but talking about reliability, consistency and durability.
It's (nearly) impossible to predict injuries or how long a player can sustain those number of touches. Edgerrin James has been equally durable and consistent despite having the torn ACL and surgery that followed.
Some players like Barry Sanders or Walter Payton can go (almost) their entire career without any serious injuries, but if I were to have a concern with LT in 2006 it would be a combination of showing some signs of weakness in his armor and more defenses focusing on him. That is, until/unless Rivers makes them pay and then it's a moot point.
We've also seen several QBs sit their first couple years and then hit the ground running in a big way in recent years. I wouldn't write off Rivers just yet. Nobody really predicted Brees having the season he did in 2004 when they drafted Rivers either. If they did, they wouldn't have gone with Rivers in the draft and just locked up Brees long-term.
Chances are, LT will be just fine.. He's amazingly durable and his running style isn't like Earl Campbell or Eddie George. So, his chances of staying healthy are at least as good, or perhaps better, than the avg RB... but when you have 2,000+ touches in a five year span it seems like the other foot would almost have to fall sooner or later.
(Now I'm sure Yudkin will roll out some super cool analysis of RBs that meet this criteria then we can look more closely at whether this is a something to be concerned with or not.. I recall similar discussion re: Ricky Williams after his 400+ carry season).