I worked at UPS for nearly seven years on three different shifts doing innumerable jobs, including loading and unloading semi-trailers, sorting parcels, and fixing international shipping labels. There are many different job positions, and many advancement opportunities. I have had friends who went into management, or became package car drivers, or even over-the-road truckers. I worked with people who have been working full-time at UPS their entire lives, who appreciated the security they received by aligning themselves with that company. It's practically future-proof because as the internet grows, so does shipping.
But, you'll have to work hard.