IIWMI'd replace bags in pairs for a 4-bag coach. If one blows, replace it and its axle mate so the pair are a known match.
Likewise for the sake of peace of mind, I'll be replacing the front two round about the 10 year mark. Riding on the rear air bag bumpers wouldn't be fun, but riding on a front would make handling a pain, maybe dangerous if it blew at an inopportune time.
Probably overkill, but a lot is riding on those front bags.
BTW, Mike from Air-Lift: Thanks for your $.02, I put your P-30 front kit in my Trek years ago and it was nice to have the features the kit included. Much nicer than stock. I'm looking for a kit to replace leaf springs on my Nissan Frontier, I'll check out your website.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project