No, not necessarily foolish. If you’re more comfortable holding on to them for a while then you should. You’ll know when it’s right to submit them.
About the holy grail of a movie placement, I’ve had a few. Remember there are no royalties for domestic theater performances. And once the movie gets to streaming on Netflix or where ever the payout is minimal. Of course a movie placement is something to be proud of, but getting a decent upfront fee is your best bet at compensation.