[Hampshire] When is it necessary to reboot

Running Debian sid means the I get fairly frequent kernel updates,
mostly 'point' upgrades.

I'm reluctant to reboot un-necessarily but do reboot when it is a major
change (like when it went from 2.6.37 to 2.6.38) but should I also
reboot on the more minor upgrades?

Incidentally I was surprised a few days back to have a message pop up
telling me I needed to reboot to complete a software update. No idea
what that was about and I ignored it ;-)

--
John Lewis
using Debian sid