I only use SpamBayes at work. My e-mail address there has remained unchanged for 8 years or so. Said address is also present on at least one publically-available web page (maybe more), so it's not particularly isolated from address "harvesting". Add to that some of the shenanigans way back when that involved collection of information from the address books of victims, and it's no surprise that I still have spam coming in - between 200 and 300 messages a week, perhaps. With SpamBayes, it's just not a problem for me at the desktop level.

For personal use, I have a Yahoo account that I've used for over 3 years. I use the address freely (have never used "throwaway" addresses), and have never used a spam filter on the account. Somewhere along the way, it finally must have found its way to some spammers, but it still only amounts to a handful of junk messages per day - so small an annoyance that I can't be bothered to do anything about it.