Pumping once/day?

I’ve been EP since my daughter was 2mo old and started supplementing with formula since 6mo- she is 8 months old now. I’d like to feed all formula and only pump once at night to have breast milk for the night feeding only (just easier to feed than mixing formula). Right now I pump twice daily and get 10-12oz/day. Has anyone gone down to pumping once a day? Did you get any milk just pumping in morning or evening? If so, how did you wean down to just once/day?

I need at least 3oz for the overnight feeding.

TIA!