SD Card 24/7 Constant Recording Time Significantly Decreased

I have a POE doorbell with a 256 GB SD card. It’s been in operation for a little over 18 months. When I first installed the doorbell it would retain about 2-3 days of 24/7 recording. Currently it only holds about 9 hours. I have noticed it slowly decreasing over time but I assumed it was due to various changes in firmware and auto changes to HDR or other settings that potentially took up more storage space. But I feel like I read that the new firmware has better storage algorithms allowing for longer periods to be retained. I messed around with Reolink’s storage calculator and it seems something is definitely not right as I should get at least 2-3 days. Now I’m starting to wonder if the card itself is just decaying? Anyone have any ideas?