I lucked out, my 1999 F350 DRW came with Airbags when I bought it in 2007 (so I have no idea how old the airbags are). I have never had any leak issues or trouble. I did break a mounting bolt once - after a rough off road trip. simple repair.
Learned a GREAT advantage of airbags this year. Never had to worry about height. But moving into my new storage barn and thought I had clearance issue. Was thinking about all kinds of works arounds. Then Daha.... Let the air pressure out of the bags lowered by about 3" giving me just enough to squeak into the barn.....very carefully - only about 3/4" clearance on my A/C unit which I rarely use!
I have been sold on airbags for a long time now. Especially with the cab control. Calms down my TC roll going down the road. I and can always adjust the ride with or without the TC on loaded!