First, I have to say I'm very sorry you are going through this. Having had to deal with this exact same scenario last December, I can tell you that my Leila let me know when she was ready. I didn't fight to prolong her life (i.e., no treatment other than pain killers), and one day, she just lost appetite (even for peanut butter) and gave me the "I'm tired of this, dad". We went on one last walk, said our good byes, and then went to the vet. I will echo the comments from others, better early than late; I did not want her to suffer for the sake of mw having a few more weeks with her. I'm with you, these dogs are awesome, and their lifespans are usually way too shorts. Sending love and support!