I'd call it a bit of overkill for a cautious, savvy user. Spybot S&D doesn't work nearly as well as Malwarebytes these days, and I've found TeaTimer to be intrusive. On my desktop machine, I run Norton AV 2010 behind a good hardware firewall/router (Netopia ENT-3386), and every other week or so I run Malwarebytes. I also have a modified HOSTS file to speed up page loading. On my laptop (dual-boot Vista Business / Windows 7 Pro) I run Microsoft Security Essentials.

Oh, I do keep a desktop computer, separated on its own VLAN, that I use to try risky web things or run risky programs, and I sometimes mount other hard drives in it to scan them (e.g., they have a Trojan or virus that prevents them from booting or running normally).