Kittens need worming on a regular basis (3 weekly ish) until they're about 6 months because it's normal to assume that all kittens are born with worms and the wormers that are used with little kittens emphasise on being gentle on little tummies, rather than being 100% effective. After that age, if they aren't going out, hunting or catching fleas then I would just worm yearly as a precaution.
However, if you're sure that the kitten doesn't have fleas, your house doesn't have any fleas and you have no other animals which could bring fleas in then I wouldn't cover them in flea treatment without evidence of fleas existing.
If you have other animals or have had other animals in your house recently (or have moved recently) then there could be flea eggs deep in your furnishings which can remain alive for months or even years, and that's a source of future infections, so keep checking regularly.
Insecurities are about as useful as putting the pin back in the grenade.