How do you know when it's time to say goodbye?

[SabineUndine]

My cat's in his late teens, and increasingly doddery. He seems happy enough in himself, spent all day in the garden while it was warm. However he has got the usual kidney and tooth problems of geriatric cats. So, how do I know when it's time for that one-way ticket to the vet's? Will it be obvious?

Yes I think it becomes obvious.
They start to retreat from life.
Your vet should also be honest enough to say when no further treatment is the best course of action

With my cat she just couldn't get comfortable, was off her food, not going out at all, very subdued. So yes I think you do know. The vet advised it was time to let her go

My vet said when they are struggling with continence, aren't enjoying their food, aren't following their usual routine or aren't wanting a stroke any more...then it's time to have "that" conversation...My 2 were doddering around for quite a while before reaching that stage (both were 18)