Managing customer history through mailing lists

Up to now I've used mailing lists to manage my customer history. Online customers (one list), and each in-person show is another list (by show and date). I now have more than 20 lists as I've done more than 20 shows, so I've maxed out the SSpace option for sorting my customers by where they have met me. Does anyone have a better way to do this? I frequently wish to send marketing emails only to customers who have bought from me at this location or that location. How can I organize my customers so I can segment by their buying history and location?