My old dog is blind and deaf. When is it time to say goodbye?

I'm sorry to hear that both you and Valentino have had to deal with these challenges over the past few years. Dogs can usually adapt fairly readily to a loss of either vision or hearing, or a minor decline in both. Complete loss of both hearing and vision can be quite challenging and many dogs can experience a good bit of associated anxiety associated with this dramatic change in their lifestyle. I agree with you in that it sounds as though Valentino's quality of life is likely poor as a result of these changes. Deciding when to euthanize is an exceptionally difficult and personal decision because there are so many factors to consider. If Valentino still seems to enjoy your company and is able to do his normal things (e.g. find the water bowl on his own, play a bit, navigate your home without too much difficulty, etc.), then it may be worthwhile to give him a bit more time. However, if he seems overly anxious, fearful, seems afraid to move around too much, repeatedly bumps into things, or has trouble finding his water bowl, then it's likely in his best interest to consider humane euthanasia. I've included a link to a guide that I personally find quite helpful in helping to decide when it's time to euthanize my own pets, as it helps me to think about things more objectively. I'm really sorry that you and Valentino are in this situation and wish you both the best.

https://vet.osu.edu/vmc/sites/default/files/import/assets/pdf/hospital/companionAnimals/HonoringtheBond/HowDoIKnowWhen.pdf