Anyone introduce formula just for a reliable backup?

I’m a just enougher and just bought formula to start introducing in small amounts. My 4mo old is starting daycare in a couple weeks and I hardly have a freezer stash. I’m certain I’ll get enough stored away for his first day, and realize I can pump the next day’s while he’s away, but it’s been a challenge finding time to pump any excess because he still feeds every 2hrs.

Anyway, I figure introducing a bit of formula can’t be a bad thing (aside from maybe the adjustment period). Maybe mixed with bm for a couple bottles a day or something to keep him used to it. I like the idea of having somewhere to turn without stress if I can’t build up enough of a stash to feel confident as I spend less time with him. Thoughts?