I have had two go. Both went at the same place - at the "weld" where the material is hardened during the welding. But they were the cheaper vinyl version.
I still use air cushions in the LandRover but did not like the rolling sensation on the bike.
The most comfy seat cushions I have tried are these.
Treat-Lite Wheelchair Cushion – Dan Medica South Ltd - I have one on my favourite armchair - bought it when I trapped a nerve in the butt muscles.
They now do a bike version
Treat Lite2 Motorcycle Comfort Seating – Dan Medica South Ltd which I have not tried as I had already converted the R3 seat to gel.