if you had your M1 and M2 previously there is no wait time to go from M1 to M2 to full M.
your insurance should also be rated off the date that you first got your first M1. thats how mine is, im over 10 years now.
i had mine expire, got my M1 and right back to M2 literally 3 days later, my friend just did the same thing this summer, he had his M1 for a week when he did his road test (after his 5 years on m2 expired).
i dont think he did his full M yet...he had to use my bike for his m2 because his doesnt really have signals that work...and the brake light is only ties into the rear brake. (its a chopped sportster, really badass looking bike)