MCAT scores are valid for three years. Also, 60% of applicants every year don't receive an MD admission, and I've seen applicants with 520+, 3.8+ receiving zero interview invites and preparing for their reapplication cycle this year. Considering you might have to reapply, I would take it after your senior year.
Just keep reviewing the concepts. Make flashcards with Anki and use them everyday to keep your memory fresh.