it depends on how much you feed them, or how much they are able to scavenge, placing bigger shells will help, but alot of the time, they'll still fight each other for shells
You'll be fine for now. If you decide to add either astrea or Nassarius snails these are the ones that my hermits loved. Most people get nassarrius snails for the sand bed. Do you have anything for the sand bed?
When you think about getting snails check out reeftopia. They give really great prices on volume purchases, about half to one third of the standard going price at other sites. New Page 1 I do not know why this forum puts the URL name down that they do for this site (new page 1), but it will get you to Reeftopia if you click on it (the underlined address in blue).