Thirty Something Hobbies

It's getting a bit of a worry, we don't have "I'll just go and check Bob's okay and give him a dandelion/put him to bed/give him a cuddle" we're now on "I'll just check Bob's upright" He's a very old bunny and had a small accident a few months back where he slipped off his ramp (of his fancy 3 storey hutch) and I found him when I got home with his back legs stuck but once I freed him he stretched out and seemed right as rain - but whether he's now got arthritis in his leg with the colder weather but several times now we've found him lying on his right side and when he sees us trying to get up but not able too! Each time I've tended to burst into tears and clutch him too me but after putting him upright again he gives himself a shake and looks round for his carrot/broccoli/dandelion and tucks in as if nothing happened?! I'm so torn I don't want my old bunny pal to be suffering but on the other hand he's still got a fair appetite (admittedly for less tough things as he's missing a few teeth!) I remember when his pal Molly had to be 'put to sleep' (she'd been a bit odd since I had her - never buy from random breeders!) it was the saddest day of my life standing in the vets clutching my little bunn. and using all the vets tissues. But what do I do for the best? Winter's coming and I can't bear Bob to suffer but I couldn't let him go when he still happy most of the time?!? A sad post but he's very much on my mind as we've picked him up twice this evening!