So hard to see a friend suffer

As I write this I am only thinking of one thing. When is the right time to put my 14 year old dog to sleep.
Navy has been with me since he was nine months old. At that time he was a springy, playful puppy.
Over the years he and I have been on many adventures, camping trips and outlived two other dogs in the house.
As with anyone, time takes its toll on the body. For the past several years he has had a bad back, with the vet thinking he has a pinched nerve or a compressed disk in it. That has meant I do all the stairs for him and lift him on and off the bed and couch.
More recently he developed a cataract over one eye and is virtually blind on the right side. He has also begun to be covered with cysts and bumps... but hey he is 14 (98 in people years).
He has also suffered seizures for many years. But lately they have become more frequent. In one 24 hour period last week he had three that I saw. And again yesterday (Monday) he had two, one of which saw him end up on his back while out walking.
It is so hard to see him suffer and having been a dog owner for a long time, I know the decision is likely not far off. Last week he bounced back and made that decision seem far away again.
But as he has more and more seizures, he also seems to become more unsure of where he is and has difficulty at times with things like walking.
I will have to see how he does the next few days. If he does not bounce back then perhaps the right time is just around the corner.
–Until then,
Ken