Like air bags and have had them now on 4 different tow vehicles. Probably never have another truck without them. Some kits have two separate hookup to manually put air in bags. Friends of mine years ago had one bag go down due to a rock puncture and it nearly threw him off the road. Ended up in a ditch with the truck seriously up on one side and dragging low on the other.
I now put in one tap to put air in both bags. If one bag goes flat, both go at pretty close to the same time. Rather have no bags or both bags with air than one bag filled and one empty.
I put the air tap inside the fuel filler door, keeps it clean of dirt, etc. Sometimes have to use a very short extension on the filler valve to be able to get the air hose on. Unless, of course, you use an onboard compressor. I had it once and it was both expensive and troublesome. Now I use about the cheapest 12 volt compressor I can buy that plugs into the cigarette lighter. Current one cost less than $10.00 and while a bit slow, it works fine. If it breaks, I can replace it for less than $20.00. Lot cheaper than an onboard set up, less wiring and fewer complications.