Converting frequent visitors to Members

Hi all, 

This is my first Tessitura forum post so I hope I get it right! I'm Membership and Bookings Manager at a science centre in Bristol, UK. We want to convert frequent visitors (day ticket holders) to members (annual pass holders). Annual membership is cheaper than three day visits per year. I'm wondering if anyone else is trying to actively convert frequent visitors to members. Our plan is to use a dynamic list to find people who have visited three times. We'd want the list to trigger an email just after the third visit to entice the visitor to sign up to membership and we will re-reimburse the cost of their most recent visit when they do. 

If anyone is doing this, I'd be interested if you could share your experience with:

-List criteria

-Enticing conversion copy for emails 

-General findings/success stories/key learnings

Thanks so much in advance, looking forward to hearing from you. 

Meg Houghton-Gilmour