Congratulations on that milestone.
I myself have been in the 60+ domain for more than a decade now.
I finished a very challenging metric today in the MS ride for CT. The ride took me a little over 4 hours; but I was drafting behind my son for this ride. That serves as assistance and a lot of encouragement.
Yes losing weight is a significant contributor if there is any ascent. I still have another 20# that I should lose.
The bigger key for me is keeping a solid fast cadence so that my knees do not have reason to give out on me. That is I keep a cadence in the 85 - 95 range.
The biggest key is getting out there and continue to train - intervals are necessary; albeit - no fun.