Kevin,
I have two tanks in my house (60 gallon and a 120 gallon) that are over 15 years old. I have never had a problem either one.
I would make sure the silicon is still soft and is not pealing from the edges, but for the most part they should last years.
As for the sand bed, I always move as much as possible, but some people don't think this is the best way to do it.