This is not necessarily an answer to the original question, but it depends a great deal on what the other owners are doing. I am in a dynasty league that has been around for 3 years. There are teams that drafted almost exclusively young players. One team in particular went with all youth early in the draft. He hit on some, missed on others and had many players who were rookies or still backups. He finished dead last that first year - and as he realized he was going to, as the trade deadline neared, he traded some of his older solid players to contending teams and obtained draft picks and younger players. (Incidentally, this is one of the reasons I love a dynasty league over redraft). The following year, he ran away with his division and won the title. However (and this is my point) SOMEONE will win the title this year.
There are basically three types of owners in dynasty leagues:
1) Those that want to win now at almost any cost - in the initial draft they have no problem taking a guy like Harrison instead of Colston - or Favre over Vince Young. Often times this is the owner as the trade deadline nears that will give up a draft pick or a young player with alot of upside to try to land that solid veteran who may be the last piece on a championship team (someone that may give up a Cedric Benson + Chris Cooley to pick up Gonzo for the playoff run, for example.)
2) Those who try to be more balanced in their approach. Generally, they'll try to make a run this year, but if they're not sure they'll make it, won't trade away their future. The problem with this is that if you continue to finish in the middle (much like the REAL NFL) you are doomed to stay in the middle, as you get middle-ranged draft picks ad nauseaum, until you either great lucky and win or get really unlucky and bottom out.
3) Those that will always take younger players with upside. The only problem here is that as the talent develops and moves from potential to production, these owners need to shift gears to become more like owner type #1 - otherwise they run the risk of having a team that will always be good "some day". In my example of the owner who finished dead last the first year, he switched gears and traded that #1 overall pick to land Torry Holt, who was obviously a big piece of his WR corps that lead to his championship the next year.
While in a dynasty/keeper league it's important to think about the future, if all the other owners are drafting rookies in the inital draft, keep in mind that someone WILL win this year. AP or Marshawn Lynch may be great backs someday - but LJ and LT already are. Colston could be a stud - but Marvin Harrison will probably put up better numbers this year. A team with Gonzo at TE and WR corps of Harrison, TO and Driver and RBs like ShAlex and Westbrook may not look like a dynasty team for the future - but they'd likely make a run at the trophy this year. That said, I would do whatever the other owners AREN'T. If everyone's going after M. Lynch, AP, Brandon Jackson, Greg Olsen, Brady Quinn, Calvin Johnson, Vernon Davis, etc. then guys like Harrison, Edge, Westbrook, Gonzo, Crumpler, T.O., Moss, Coles, etc. are going be available.
The inverse also holds true - if everyone is drafting likes it a redraft, then those rookies who will be sharing time or being worked in during this year will be available. If you're not worried about this year and the fact that AP may be splitting time with C. Taylor or that it may take Calvin Johnson a year or two to be stud-like, or DeAngelo Williams will be splitting reps with Foster for another year, then snag them. You can probably snag a guy like Michael Turner late - just to see where he ends up starting in 2008. If, at the end of this year, guys start to turn into studs (but your record is already horrible from having to start rookies who aren't even playing full time yet), all the better - you probably have early draft picks to shore up your team or trade for established veterans to make the charge next year.
