Out of about 180 schools, the only two I know of that specify that they "expire" prereqs are UMass and Miami.
I care about this a great deal because I took physics in 1988. I've not been required to retake it.
I suggest that you should show recent classroom success in something. If your micro degree was recent, then imho just focus on the MCAT. If you find out that some school takes issue with the age of your prereqs, first you show them your killer MCAT score, second you petition to substitute recent coursework. Worst case you might need to take a summer session course before you start med school.
Best of luck to you.