I've never had to make that call before and could do with some advice.
My cat is nearly 18. He went very skinny a year ago but the vet couldn't find anything wrong with him, he still eats an ok amount. His legs are hurting a lot though and he is getting stiffer by the day. He just doesn't seem happy any more 
Is this reason enough to put him to rest? I don't want to drag out his time here but also don't want to say goodbye to him when he could have longer.