My fiance has a plastic macbook (not a 2008) that is still supported and running El Capitan. It was running sluggishly so I too dropped in and SSD and some more RAM. The Macbook has fared well compared to my 2011 MBP which has video card issues Apple wont fix.

Either way getting 5+ years out a laptop is outstanding. I went through a few Sony Vaios in that amount of time during their hayday plus a brand new computer that had the monitor go out completely. Plus I was stuck on windows which is a big pain point for me.

Looking forward to replacing the '11 MBP once another refresh happens this year.