I've got 2 years on my 6 gallon BB and still good ( well as good as I brew that is ).
A tip for you...get yourself a couple milk crates to put them in so when you pick them up, they won't flex and suck stuff back in through the airlock.
I wish they would make a 6.5 gallon version though. I just did a 1.098 beer and came up short on volume ( 4.5 gallon ). Good thing I did because it went nuts, even with the blowoff tube. Can't image what my basement would have looked like if I had the actual 5 - 5.5 I was shooting for.