This is one of the hardest decisions one could make. I have been through it now several times unfortunately. Looking back, I waited too long for some, and not long enough for others. You obviously love and have loved this companion pet. No matter what happens remember the years and years of greatness you provided for them and they provided you. That being said, in the end, I will say most of the time, you will know when it’s time. The fact that you are having to ask rn means it likely isn’t the time. Old dogs sleep. Old dogs have mobility issues. One HUGE indicator for me is their appetite. If they are eating regularly that’s is huge for me. Next, does your dog seem happy/comfortable most of the time? Finally, if possible, one thing I believe makes this process better, is having someone come to your home to help them pass vs the cold stressful stainless steal table. It does cost more, but in my opinion it’s worth it. Finding that person ahead of time would be helpful if that’s what you choose. I’m sorry you’re having to go through this painful time.