Its your product so you can do what you like but here is a suggestion:

Offer a 30 day trial license instead of 1 week.

Lets look at some scenarios:

Customer A decides to try out your product for 1 week using $100 bucks on BTC-E. In that 1 week he performs several automated trades and maybe he turns a profit 1 or 2 of the days but by the end of the week he is under 100,do you think he is likely to sign up?

Customer B decides to try out your product for 1 month and using $100 bucks on BTC-E. In that 1 month he is under 100 bucks during the 1st week or so but by the end of the month he has earned a profit of about 15%, do you think he is likely to sign up?