Thanks so much guys, I really appreciate all your kind words. To be honest, I'm strangely OK about it all- I am pleased he entered our lives when he did and he genuinely seems fine and genuinely content so I am glad we have been bale to give him a happy retirement. He doesn't have any meds other than what he has for his CRF at present but the vet did say they could probably give him something if he goes downhill and shows signs of being in pain or anxiety. He is a very difficult cat to tablet as he will filter even the smallest pills out of his food (cheeky monkey!) and gets very distressed at taking anything so we agreed with the vet that we'd keep things to a minimum and only give him what would make him feel better. You're right Mark, they just enjoy the time they have and don't have the same concept of life-length as us, they just know when they're happy.
He's sitting next to me (well rather lying on his back legs akimbo!) purring his head off so he's doing just fine.
We're going to reassess him as we go along and it's just a case of seeing how he gets on. He may keep going for ages or it may be quicker- as long as he's happy, we're happy.
I suppose the only positive thing about him having something visual as a symptom (his lump- we call it his noggin!) means that we are aware he has an issue and so will monitor him closely rather than missing some of the subtle things cats can get with old age. When my family cat (another Monty) passed away of old age, it was only looking at pictures in hindsight that made us realise how poorly he'd been and we felt bad afterwards doing the usual worrying about whether or not we kept him going for too long? etc so at least this way, we're aware of the fact that he may go downhill and can prepare (as much as you ever can) for when that happens.
I think, as I went into our adoption of him with my eyes open, I knew he was elderly and that it could be a long or a short relationship, I think OH is finding it harder to come to terms with. Of course, we'll support each other through it but when Rufus passed, OH stayed strong for me as I was unbelievably devastated where as I think with Monty, he's sort of always been more his cat. From Monty's point of view this is because OH is there purely for cuddles, where as I have always been the meany with the brush and tablets!!! OH has such a bond with Monty because the others have always tended to go more to me and Monty was the first one who had ever preferred him. (It made him feel special I think).
However long we have left, I feel so honored to have such a lovely old gent in my life. Major Monty really is one of a kind.