Look at the sidewalls for any cracks (both sides). If you've got even small ones, you'd be better off replacing them if you're planning on going anywhere over a short trip away.
I put LT tires on our Monty shortly after we bought it as the original STs were already five years old and we planned on trips out west. No way was I planning on keeping speed down to 60 or less when every one else was going to be doing 75 - 85! They lasted five years, three trips coast to coast and two to Canada. Total over 40k miles. Tread still looks great, but there's slight cracking on the sidewalls (probably from the stresses of tight turns), so they're gone and we've fresh LT rubber, all four less than six months old.
If you read the very small print on an ST sidewall about loading, many of the E range ones limit speeds to 62mph. Don't ask me why, as it makes no sense.