If your supervsion you don't have a thing to worry about, your covered forever and ever. My local however started a retierment security fund for drivers after brown. We used half of one of our raises to get it started. Just for UPS drivers tho. Other than that i think you get no bennies once you retire from UPS-out here in California anyway. at our contract reading they told us health and welfare cost like 1400$ a month(pension included).
BTW it takes 60 months of paying into the fund before you vest into it. At its inception it was 24 months, but since healthcare costs go up like 18% a year, who knows. And the benefit is50% of what you got while working.
Hope this helps