I know this is a frequent question about integrating trial limitations to people's projects, and this article provides a stellar base to see the lay of the land, what's works where, and to find the best fit for your program. It won't solve all your problems but it will sure give you a place to go!
A good trial is a balancing act. You need to give prospective customers enough to show them your software could solve their problem, but not enough to actually solve their problem. But if you are too restrictive they might go to a competitor with a more relaxed trial policy. It can be tough to get the balance right or to know whether a different approach would get better results.