First, I would suggest to use only industrial grade SD cards like WAGO’s.
They have up to 20 000 write cycles per cell and up to 10 years data retention.
The max number of writes is a number per cell, and not for the whole SD card of course.
The lifetime will depend on many factor like the free space available (the more there are the more the writes are “spread” on different cells), the temperature, the number of writes indeed.
I would also recommand to use a buffer that you can place in RETAIN memory, then the data won’t be lost if a power outage occurs. It will reduce the number of writes a lot.
Additional hint, consider this to take a look to the status of yoru SD card (if it supports S.M.A.R.T)