Offroading coud speed up the death of the air system but they are just known for problems and inevitable failure in general. Your air suspension may be fine for a long while but here's the issue: replacing a leaking air spring will cost almost as much as converting the vehicle over to coils. Even if you replace an air bag, a more expensive component (like the valve body or compressor, or another air bag at that) could, and is likely to, fail. It is universally understood among classic owners that the air suspension isn't worth putting money into and coil springs are superior in every way. The likelihood of failure is very good and with the coil spring setup, you don't lose any handling or off road capability. Granted, the air suspension could extend beyond its normal paramaters to get a high centered vehicle un-stuck but with the right spring setup, you can find a very nice balance between ride, handling, and offroad capability. Atlantic British Ltd. is a great parts supplier for rovers and has coil spring conversion kits available for classics. I bought my conversion kit from them selecting Old Man Emu springs over the stock springs. I believe the kit was $399 (including more expensive springs). The dealer converted my truck for about $900 and i've never looked back. Good luck with your purchase.