Fergie,
It doesn't look like the "whole" story has been told to you. Here it goes...
A RCA works their way up the "seniority" ladder within the office that they are assigned. As regulars leave the Post Office, routes are first offered to other regular carriers in that same office. Once all regular carriers are where they want to be, the "left-over" route is then awarded to the senior RCA. (If they don't want it, it then becomes available district-wide)
There is no easy way to become a regular carrier. In order to work your way up the ladder, you need to stay in the office you are assigned to...otherwise you loose (YES LOOSE) all your seniority when you start at another office.
You need to take a look at where you are right now. If your office doesn't have a seniority list posted, you have every right to ask for one. It's not a science, but you can kind-of figure out how long it will be until you become regular by the number of routes, the ages of the regulars and the number of RCA's ahead of you.
After one year of service, you are eligable to transfer to other offices. (again, you will start from square one). But if you check into other offices around you (using my not-so-exact science above), you may find that you could possibly become regular quicker. It ALL depends on those factors, and isn't a guarantee.
Good luck to you...I hate seeing another RCA that wasn't educated about this dang job!
Mac