I work as a teacher at my former middle school. Yesterday I came into possession of the old band teacher's 15" 2010 MBP, a fantastically beat up base model! Many, many miles and battle scars on this machine but she still works beautifully. I took it home, completely gutted it to clean every nook and cranny, refreshed the thermal paste, installed new feet, put in an SSD and 8GB of RAM and it's running High Sierra like a champ! I may play around with upgrading it later using OCLP but I'm really loving how HS runs on this first-gen i5
Even the original battery is holding up great at around 500 cycles and 80% health, not too shabby for a battery that hit its 13th birthday this summer!
Hey congrats on the find! These little machines are amazing. I had a 2010 unibody MacBook for a time I was doing the same with and it was hanging in there pretty well.
If you do decide to make the jump to OCLP, one thing to note. If your machine doesn’t support Metal, a lot of apps aren’t going to work. Safari and Pages/Numbers/Keynote and most system utilities are fine, but Maps, AppleTV, Find My, and others won’t work properly. High Sierra despite its EOL status may still be the most complete functional experience, but it depends what you want to do with the machine.