The following suggestions represent the minimum number of visits I believe your pet should receive when you’re away. There are some additional considerations listed after all the cute pics.
PUPPIES UP TO 6 MONTHS OLD

PUPPIES 6 MONTHS TO 1 YEAR

DOGS OVER 1 YEAR

KITTENS UP TO 6 MONTHS

CATS 6 MONTHS AND OLDER

Additional considerations:
How long will you be gone? How many pets do you have? What are their personalities?
If you’re going to be gone for longer than a week, I recommend throwing in some additional visits here and there. This could mean the occasional overnight stay, or an extra visit in the middle of the day every few days, or several visits of longer duration.
If your cat is the only pet in the household and is highly sociable/affectionate, and you’re going to be gone longer than three or four days, I recommend two visits a day. This also goes for cats with lots of energy and a tendency to zoom about the house bouncing off walls.
If you have a truly anti-social cat or dog who is traumatized when anyone other than you or your family members come around, fewer visits may actually be more beneficial. For cats under these circumstances, I think you can get away with visits every other day, although I still prefer at least one visit a day because stuff happens. For dogs, it is a bit more complicated, and I would consult a behavioralist or qualified trainer when devising a visitation plan.
Boarding
I think there are circumstances in which your pet may be better off at a reputable boarding facility.
Puppies who have all their immunizations may be happier in an environment where they can interact with other dogs under supervision.
Although many pet sitters will administer medication, if your pet is critically ill, or has a newly diagnosed condition such as diabetes or asthma and has not yet become regulated to his or her medication, or is particularly hard to pill, I think a medical board at the vet often makes the most sense.
Environment while you’re away
It is particularly important that puppies and kittens are confined to a small room or pen in between visits from your pet sitter. This area should be free of anything that could pose a choking, strangulation, or drowning hazard (this includes many toys, loose blind cords, and toilets with the lid up). This area should contain comfortable bedding and safe toys (think stuffed animals for kittens, and Kongs for puppies) and an article of clothing with your scent on it.
*All photos in this post are courtesy of Pixabay.