> It gets sluggish if I don't. > ... Netbeans IDE, Safari (and a bunch of tabs), Firefox (ditto on the tabs), an FTP client, a Subversion client, iChat, Mail, a notes app, alarm clock, Dropbox, Evernote, terminal, one other text editor (MacVim or Textwrangler), Photoshop, MS Word, a clipboard app and sometimes VirtualBox

Did you check top? free? You should be able to see what's eating your machine after a few days of uptime.