If you go from part time to full time, any part time years in which you worked at least 500 hours will count towards your PEER 80. Your pension benefit will be calculated accordingly.
I did 27 days more than I had to (30 years and 27 days) just because it took the Union that long to get it to me in writing that I had met all the requirements for a full pension. I insisted on it in writing because by the time I had 30 years in didn't trust UPS or the Teamsters word on anything.