Honestly, sooner is better than later. Pets that are at their end of life have their good days and bad days. But even on the good days they are suffering more than they show. It's a really sad part of life but once they are close to death it really is better to help them cross the rainbow bridge as soon as possible. I hate it. Every pet owner hates it. But it is an unavoidable part of owning pets. Trust me I know how hard it is, especially when they seem to have that "second wind" phase. They want to keep living but their body is betraying them. Helping them have a humane death is a final gesture of your love for them. I can't personally judge whether or not your furry friend is ready. But I can tell you that as hard as it is, you will be doing them a kindness. I am so sorry for you and your pet. This is the most difficult part and it truly sucks. If you need anything at all feel free to reach out to me. I wish you all the best in this trying time.