Tried a gel pad for awhile. What I found was with the gel pad I was able to ride a little longer, but not much. Like you I could go about 60 to 90 minutes. With the gel pad I could go just about 2 hours. On the longer rides I would swap it out. Started with the pad, took it off when I got sore. The change of pressure points allowed me to go about another hour. Then I'd put it back on and could go another 45 minutes or so. The time between got shorter and shorter.
I thought about getting an inflatable pad but after reading a bunch of recommendations I ended up getting a Mustang wide tourer. I can ride all day with it. Still get a bit sore but nothing like before.
Sometimes life seems to be delivering punches,
When in all reality....
It's delivering wisdom...
'08 Shadow Aero
General Disclaimer: I've been wrong before, I'll be wrong again. There's a chance I'm wrong now!