My 2009 13" MacBook Pro still runs great after all these years of heavy use. I've cleaned it and reapplied thermal paste on the CPU/bridge chips twice.
> reapplied thermal paste on the CPU/bridge chips twice
does it help noticeably?
I recently reapplied the thermal paste on my 2015 13" MBP. It lowered CPU temperatures by about 5°C so fan noise is only slightly diminished, but it's no longer crashing under load on a weekly basis. And this was using an old tube of cheap paste I had lying around for years.
What does re-applying thermal paste do?
It improves the transfer of heat to the heat sink, cooling the CPU.