One very important note to add:
After transfer, for preferred PT Jobs (Clerk, Smalls, Irregs, etc.), you're basically screwed--those are all based on CENTER/BUILDING Seniority. You'll go back to 0 as soon as you transfer.
However, for Full-Time jobs, many of those are based on COMPANY Seniority. So if you started in, say, January 2008, transferred in January 2012, and in February 2012, a FT Job comes up, you won't be putting 1mo seniority, you'd be putting 4 years 1 month.
Do your research, and take your time. You don't want to go from average-seniority and working every day, to low/bottom-seniority and possibly only working a few days a week, especially if you're still going to be a year (or two...or four) away from going FT.