Recently purchased a house built in 2006. The shower gets colder as time passes and requires constant adjustment of the valve in order to maintain temperature. I replaced the cartridge in the valve with a brand new one, and the problem persists. What else could it be?
I have heard it can have something to do with hot water recirculating pumps as well, which I do have installed.
EDIT: I know I'm not running out of hot water because I can use the adjacent faucet right after the shower and get hot water.