I know you're new to this, and are trying to "plan" ahead for your career... but if you are falling for the myth of regionals being stepping stones to major carriers... you are in for a rude awakening.

Most majors have not been hiring, the few that were this past year are now basically furlough fodder. Regional managements have been getting wealthy off of new hires willing to take a job for next to nothing pay because they "will only be here a few years." The reality is that even if you got in right now... you will spend the majority of your career at a regional. The mainline carriers are shrinking, consolidating or going bankrupt. The managers do not want to grow the legacy carriers. They would much rather let them go BK, and replace them with workers who have already proven they will work for next to nothing.
So, five or six years when all the 60+ folks start hitting 65 and there are massive openings at whatever remains of the legacy carriers, those seats will be filled by people who started four to five years ago. The folks with more time will have already been regional captains, in seat, for several years and likely unwilling to take the drop in pay to first year new hire at whatever is left of a legacy carrier. So, the 2-5 year captains will be the most marketable, and will still be in a pay category that they "could" take the paycut for a few years. The 3-9 years FO's will have enough time to meet the higher min's required for SIC only time, and will definately take those jobs. So, unless you are in like right now.... or perhaps within the past year it would be best to plan for a regional career... unless you know somebody high up that can not just walk you in, but tell them to hire you above others.
Look through the Boyd Associates and other industry watchdogs and you will see that the growth will be in the regional carriers, while mainlines continue to shrink, merge or go out of business.

So, when you do come on board at one of the regionals, please do not be one of these new hire tools that doesn't care about the union, and doesn't care about upholding the contract. The regional job will be your home for some time. If you are not at your major job by the time you have been upgraded for a few years, in all likelyhood you won't leave.

Upgrades come when your seniority number is reached... as long as you have the minimum times you upgrade in turn. There are plenty of examples of FO's with 15,000 hours that have not upgraded due to no movement at the majors... and around 9,000 at some regionals. It rarely is about hours... mostly just when your number comes up. 99.5 percent of the time, by the time your number comes up, you have enough time to upgrade. The places that occasionaly hire street Captains are the places you probably wouldn't want to work for anyway. If their turnover rate is so high that they can't keep people long enough to have enough time to upgrade what does that tell you about the company? In some cases they are hiring people with fresh multi instrument commercials who have less that 250 PIC... these folks can NEVER upgrade... be careful when selecting your employer.