To be honest it is a slightly stupid question and I don't think your "three updates" rule works for Macs at all - iOS maybe but not macs.
I have a mid 2009 model - yes a whole two years older than yours - and it certainly hasn't been murdered by Yosemite, in fact there's no noticeable performance drop from Mavericks. And like Mavericks it's still *kinder* on the battery and a lot more feature packed than the Snow Leopard my computer shipped with. As an older Mac it doesn't get Handoff, but I still get to answer and make calls on my mbp now which is pretty cool.
No if my question was a legit question.