Well that is a matter of opinion. Most breeders use pinkies at least once a month. Treat they are not they are packed with everything they need. They will help build weight and get them healthy. Once a month would be just fine and yours is under weight then even twice a month till weight is not a factor.
Its not likely they will get "hooked" on pinks. Its more like good luck trying to get them to eat one. Usually very small works best.
The fact is that many breeders use the pinks to build weight and keep them healthy. Not as a treat.