What types of topics have you folks come up with for the monthly newsletter drip campaign?  The basic campaign has some good generic topics, but once the first 12 months are done.......then what?  I use it primarily for my past clients, but I'm also working on a different one for my contacts/leads/prospects who have NOT used me yet. 

  I'm trying to tweak it to run for at least 24 months, but am having a hard time coming up with topics that are interesting and pertinent without being redundant.

Any suggestions, or comments on what you've done with your drip campaigns?