Sorry to bump this but am just getting caught up with all the "historic" posts on TV.
My parents planted a spearmint in a pot in their rock garden. It was bounded on two sides by boulders and has escaped the pot and been spreading from the nook, in spite of an arid zone 4 climate. I think it's safe to say not to count on frost or drought to relieve you of your mint problem.
I'm intrigued (okay, maybe it's my stomach talking) by the suggestions for mojito and chocolate mint uses. As these are not good from seed, where/how would i go about getting these?