Just for my own curiosity, do you trust your spam filter on your email?
What I mean is, if something gets marked as spam do you feel tempted to open it and see if it is, or just delete it.
Generally speaking I make use of webmail and I check headers of any incoming message. If it looks safe, I open the mail otherwise it goes to the trash. Mail flagged as spam generally are, but for a few cases I checked them as outlined before and decided to keep them.
I've to say that I receive very few spam messages (less than 1 out of 50+) and wrongly flagged ones are no more than 10 in a year.