- 4 bytes of data every 2 seconds wont have any noticeable life reduction of SD card

The filesystem block size is 4096 so that's how much gets written every time a file with 4 bytes of content is overwritten and due to the overwrite, the same inode is being used every time. With two files, that results in a constant 4KB/s write on the sd card. Unless it does wear leveling internally (that appears to depend based on the make and model, somewhat hard to find exact details), such usage is sure to reduce the life of the card.
Ill do some more research and see if this is something of a concern for a time scale of a few years, its easy enough to switch to a ram disk either way.
We have some interesting stuff planned down the line thats even better than some api backend (think server login/remote control/mass configuration/mobile control

)
Thanks, looking forward for the next release.

The workaround (or fix) for those two files is indeed simple:
cd /var/local/apollo/hwmon
mv fan_rpm /dev/shm/ && ln -s /dev/shm/fan_rpm fan_rpm
mv pcb_temp /dev/shm/ && ln -s /dev/shm/pcb_temp pcb_temp
I also noticed there's a service configured looking for a serial port that isn't available so disabling it stops warnings getting constantly logged (commands as root):
systemctl stop "serial-getty@ttyS0.service"
systemctl disable "serial-getty@ttyS0.service"
My Moonlanders are finally connected to the Apollo so no more need for a separate Raspberry Pi:
