Why is lora.nvram_save() not writing to RTC RAM?

[KenM]

You have to save it after each Lora connection/wake-up so it's not a setting that you just (write)/read 1 time after power-up.

There is also no point in keeping it saved after power off.
RTC RAM is the right choice. (is not erased during deepsleep)

Does someone know about how much bytes we are talking about for the lora save? I assume it won't be much.
There is 8k RTC RAM, not sure how much is free?