I will only do 15 to 20 mins of pumping either before/after latching. I dont do power pumping. And my pumping schedule will be every 3 to 4 hrs. It can be hurtful sometimes or nipples get painful. Also after every pumping and latching, ill put nipple moisturiser.
How long have you been pumping? Maybe need to check whether you are using the correct flange size. For me, it's only sore a bit for the first few days. Now I can pump 20 min with no issue.