He didn't have quite as much longevity as I'd like. He fell off pretty bad from the 2008 season (at age 29) onwards
If he had put together 2-3 more 1500 yard seasons, he'd have a very strong case
But then again, running backs fall off at relatively young ages:
LT had his last very good year at 28
Walter Payton had his last very good year at 32
Eric Dikkerson had his last very good year at age 29
OJ Simpson had his last very good year at age 29
Emmitt Smith had his last very good year at age 31
Barry Sanders was very good his last year at 30 (we don't know how the rest of his career would have played out)
Jim Brown was superb until his last season (which he played at age 29)
It's not by much, but LT did fall off slightly earlier than the other top contenders
If he had put together 2-3 more 1500 yard seasons, he'd have a very strong case
But then again, running backs fall off at relatively young ages:
LT had his last very good year at 28
Walter Payton had his last very good year at 32
Eric Dikkerson had his last very good year at age 29
OJ Simpson had his last very good year at age 29
Emmitt Smith had his last very good year at age 31
Barry Sanders was very good his last year at 30 (we don't know how the rest of his career would have played out)
Jim Brown was superb until his last season (which he played at age 29)
It's not by much, but LT did fall off slightly earlier than the other top contenders