What Goose said!
There are way too many variables to accurately predict how long you will have to plumb on the panel before you can jump to a window seat. I would guess, however, that if hired today it would be at least 3 years and possibly 5 before you would move off the panel. That could change if you are hired next month and the 150 or so vacancies in the back are filled right after you get here. That is why it is just about impossible to say how long you will have before upgrading.
I have been here almost 2 years and still can't hold a line period, let alone a "garbage line". Then again, there are guys who hang out in the back for 5-7 years by choice because they enjoy the relative seniority in that seat. There are a lot of different types of flying lines at FedEx and what is good for someone in Memphis may really bite for somebody commuting out of Allentown, PA or Spokane, WA.
As for reserve lines, there are 3 types. 'A' reserve (generally the most junior) is for mostly am flying, and you are on call from midnight to noon. 'B' reserve is mostly for pm (FedEx pm anyway) and you are on call from noon to midnight. It tends to go just slightly more senior than 'A' reserve. Both of those have 1.5 hour report times, but can be shortened to 1 hour if you are given late call parking right outside the AOC. 'RSV' reserve has a 24 hour report time and tends to go the most senior and is naturally favored by commuters, who can wait until assigned a trip to start their commute into Memphis. Once assigned a trip you are pay (with substitution) and discipline protected if you have a reserved seat on a company flight for your commute.
It should be noted that even on B reserve, all they have to do is have you report between 1:30 pm and 1:30 am, so there is still a fair amount of backside flying on B reserve. Some trips start on a Sun afternoon, fly to an outstation, layover for 24 hours and then fly am hubturns for a week before going back to the planet. And when schedules gets really devious they can expand the am flying by having you report at 1:15 am, which sure feels a lot like backside flying (because it is) but falls within the 'B' reserve report time.
All of the lines are bid upon each month based on seniority. The lines are published in the bid pack, you throw your choices in on the computer, and it spits out your award about a half hour after the bid window closes. After the awards are out, the computer starts dropping trips for people with vacation and training, creating open time for secondary lines and plain old open time. So you can bid a week on, week off line during a month in which you have vacation in order to have those vacation days knock out one of those weeks of flying, which gives you 3 weeks off in a row.
With a preferential bidding system (as I understand it) you would bid which weeks you wanted off and the computer would build you a line around your "vacation" or training and so you would still have to work 2 weeks that month around your "vacation". In other words, you would just be getting time off that you would have had anyway based on your line and not really getting any benefit of the vacation days. PBS will not fly with the crew force at FedEx in my humble opinion.
I hope that info helps. Other purple people feel free to weigh in on anything I goobered up.
FJ