Background: hobby coder running Raspbian on a Model B.
I've deployed a RPi in my brother's garage. It connects to a few temperature / moisture / etc sensors (via Python, over a serial connection) and records readings to a mysql db. Every half hour it averages these readings and POSTs to a little REST API I wrote on my server (after which it deletes the transmitted rows from the SQL DB) - the server then draws some pretty graphs.
I would like to interact with the unit as little as possible moving forward and have a few questions about how best to achieve that. Let's pretend - as unrealistic as this may be - I'd like it to be plodding along doing the exact same stuff in 5 years time.
Reboots - I've noticed the Pi slows down after a few weeks of use, so I've got it restarting automatically every 14 days. Is this normal? Should I expect that 14 day interval to drop over time?
Free space - I have an 8gb SD card. Practically, I'm never going to fill that up. Academically, I'm sure that if I measured free space ~1 week apart there would be a decrease because of various bits of logging that Linux core (and Python and cron and MySQL) get up to in the background. Is there a way I can stop this? Should I? Is Linux clever enough to set a TTL on these logs or delete them if it starts to get low on space?
Hardware - Is it fair to expect a few years of continuous use out of the Pi before the hardware starts failing? The only relevant factors I can think of are a) it's in a little dust-shielding case, but b) it's not very processor-intensive work, so it runs quite cool.
Appreciate any ideas!