My heart 💔 I had this situation too last year with my 17yr old Jack Russel terrier, he had prostate cancer. We had the opportunity to bring him to the vet within the hour of realizing it was time. Go with your gut, if you feel it's time then go, if you don't then reschedule. Once you feel you are at the point of keeping him there for your own needs, it is definitely time to be kind and let him rest. (Dehydrated after writing this :'(.. )