I would start with a couple varieties of snails to start and skip the hermits. I had too many dead snails from them. You can more snails later as your need increases.
10-Nassarius Snails : Great detrivores and sand-stirrers. They will hide in the sand until feeding time.
5-Cerith Snails Will also breed in your tank. Good algae eaters and sand-stirrers.
Snails need acclimation time to adjust to changes in salinity and temperature. Dr Ron's advice is, "Remove them from the bag. Let them dry out in a cup or bowl for about 15 minutes. Then take them one by one, and place them in the tank at the water line with the aperture next to the wall. The animals will extend, fasten to the wall and move into the water of their own accord. In effect, they will self-acclimate." I've done that with Nerites but not any others. Other snails I drip acclimate for a couple of hours.
I like nassis, ceriths and nerites. Always start with a lower number, because newer tanks won't have enough food for a large number to graze upon. I tend to stay away from a lot of hermits. I have three in my 55, just make sure you have larger, empty shells for them to move into.
Age is relative, you are only as old as you act....of course, this works in reverse....