Both of my girls are tested and registered with Therapy Dogs International (www.tdi-dog.org
I like Therapy Dog work a lot - love going to visit with people. When we lived in northern Virginia, we visited an old folks' home that had a special program for the memory impaired with Abby. We met a lot of very interesting people there and Abby enjoyed being around the old ladies, who would pat and scratch her and talk to her.
When we lived in southern Virginia, we visited with the Warrior Transition Unit and some of the other units in base, and that was great, too. It was much more relaxed than the old folks' home because we were visiting young soldiers, so it was always pretty fun.
Now that we're in northern NY, we're trying to set up an official therapy dog program on base, at the hospital and the WTU, but it's been slow going because they've never had such a program and are not really sure what requirements the hospital has for the dogs, and all that. Hopefully we will be able to get everyone together and talk about that.
Different dogs will like or dislike the work differently. My Abby likes visiting and likes being petted, but she does not have the same "pet me pet me pet me I love you" vibe that Ronja, my Malinois has. Ronja will hear a person say the word "DOG" and she will turn around and snuggle into their lap and stick her head into their chest for scritching. If Ronja had her way, she would crawl INTO your lap. Anyone's lap. As long as they pay her attention. And she also has a lot more endurance for visits than Abby does, who needs frequent breaks and really can't go longer than an hour. Ronja would visit ALL DAY if she could.
As far as hours and commitments go, it really depends on your group. If you're visiting as part of a group, you will have set times, days, and places to go. If you're registered through TDI, or Delta, or any of the other big organizations, you can approach hospitals and old folks' homes on your own and schedule your visits through them, usually through the activities or volunteer coordinator.