I’ve found that companies often remove people from their databases far too soon — especially considering the potential lifetime value of the prospect and his company. 
 
If your customer only buys once in a lifetime, then keep him or her on your database only until they buy from you or a competitor.
 
However, if the contact continues to buy the kinds of products or services your company provides repeatedly, consider leaving the person on your database forever. Or leave the contact on your list for as long as you know you can still cost-effectively get your marketing messages through to the person by mail, e-mail, fax or phone.
 
My clients frequently tell me that they are now closing first sales from prospects who have been in their databases for two, three, four or more years.
 
One way to determine if keeping prospects and customers on your database for a long time is cost effective is to compare the annual cost of database marketing to one prospect or customer compared to the cost of finding a new one.
 
For example, if your company spends an average of $250 to generate an inquiry, but only $25 a year to keep in touch with each contact through database marketing, you can afford to keep the prospect or customer on the database for up to 10 years for the same cost.
 
If you’re going to keep contacts and companies on your list for a while, I suggest that you occasionally ask the contacts if they are still interested in hearing from your company. Tell them, if they don’t respond, you’ll remove them from your list. Keep those who say “yes” on the list. Then remove those who fail to respond. Better yet, keep the non-responders’ records for statistical purposes, but code them to be suppressed when pulling lists for mailing, faxing, e-mailing or calling.