I second Willie's recommendation. Hard to beat for $18.
It can be configured in many ways from high quality to low and all files recorded don't have to be the same bit rate, sample rate or type. It can do .mp3 and other slim file versions. We use 16-bit 40kbps at 22.05 kHz sampling mostly.
The music station gets Stereo files at around 56kbps, while the morning show get 96kbps 44.1 kHz sampling but in Mono, the higher rate in case they wish to make promos out of something that aired.
I use hour-long files. We lose about 15 seconds at the end of each hour. This could probably be reduced if you used half-hour files as Willie does.
You could program the scheduler in it so that it begins overwriting old files after three months. Not sure how involved that would be to set up (not complicated but could be very tedious). We only have 24 events in the scheduler
that repeat everyday but save the file with a time and date stamp so there is no overwriting. In other applications we have found the schedule will hold LOTS of events.
Salem Media Group Omaha
.KCRO 660 AM 106.5 FM The Word
.KGBI 100.7 The Fish®
.KOTK 94.5 FM 1420 AM The Answer
Using StationLogger XE and works great. Yearly license but records up to 4 sources all with 1 hour files. Works well.