dropping a pump

hi! i am currently EBF my 2 month old. i pump 7am 10am 1pm 4pm 7pm and 9pm and get around 38oz. i pump for 30 minutes each time. i don’t pump at night because i get enough during the day and he has been sleeping thru the nights. i’m wondering how much my supply would be affected if i decided i wanted to drop one of the pump sessions or maybe i should change my pump schedule up. also i’ve always pumped for 30 minutes because that’s what was done in the hospital but should i have started for less time and then increased to amount when i wanted to drop a session?