Sooty was nearly 20 when he passed away in the summer, I had a series of storage crates of different heights which I glued a piece of carpet to, and we used these as steps all over the house - only the sofas, onto the bed, and on either side of the cat flap. They certainly made life a lot easier for the old chap!
PS My new cats have temperature microchips, it reads their body temperature as well as the chip, thus avoiding the need for the vet to shove a thermometer where the sun doesn't shine each time she sees them! Might be worth considering for the older chap!