I took my Golden Retriever to an emergency hospital on the recommendation of my regular vet. Our dog was very sick and needed after hours care. Though we thought we were just taking him for extra care for his pancreatitis, the emergency vet actually discovered that my dog had lymphoma (cancer).
I am very grateful to be able to say that our eleven year old Lab has never had an emergency room visit. She has had an amazingly strong and healthy life.
I have been really lucky with my Rottweiler, but did have to take him in for emergency care due to an enlarged prostate that pressed against the nerves in his hind legs. He got bad really quickly and couldn't walk. This caused actual nerve damage and he had to be have physical therapy after being neutered so that the prostate would shrink. We did physical therapy for 1 1/2 months and now you would never suspect that he had ever had nerve damage!
My old Lab had cancer in his jaw. I took him to the hospital after he started yelping from eating.
also see 9 Symptoms That Require an Emergency Vet
also see Finding an Emergency Veterinary Hospital When On the Road
also see 3 Vet Questions Dog Owners Don't Ask—But Should
also see Emergency Pet Hospital Insurance: What's Covered and What's Not