I play in a keep up to 3 players, for N+3 years from acquisition. These players are kept at the acquisition price, the round where they are acquired. No player drafted in the first 3 rounds can be kept. A waiver add that you keep is a last round pick for N+3 years from WW acquisition.
I love this format, and you try to absolutely score on WW picks, and guys drafted after round 3. However it shakes out, you take the most value available, and build next year's team around that core. Doesn't matter so much each player's position, but how much value they present to you to allow you to draft key players at other positions and be in "win-now" mode each season, if your keepers pan out.
An example to play this out, going into this season I kept:
- Jimmy Graham as a WW add before the 2011 season when he broke out. He is in N+3 as a WW add for me, so I have to release after 2014 to the player pool.
- Randall Cobb as a WW add from the 2012 season when he broke out. He is in N+2 as a WW add for me, so I have him through the 2015 season, then must release after 2015 to the player pool.
- Andre Ellington as a WW add from the 2013 season, entering 2014 as the starter. He is in N+1 as a WW add for me, so I have him through the 2016 season, then must release after 2016 to the player pool.
Having locked up an elite TE, high RB2/low RB1 (opinion withstanding), and low WR1, I had that as my situation to build around. I never draft QB's early, but these keepers gave me the ability to do so, and I took Peyton Manning 7th overall. Then just took best player available after that at RB/WR the rest of the draft since I'm not drafting backups for QB/TE in a situation like this. Season has gone great, and I focused on younger players after round 3 for future keeper "mining" while still playing for the playoffs.
Don't lose sight of prospective keepers, as I kept 2 guys going into each of 2012, 2013, and 2014 that I didn't continue to keep due to performance/ circumstance/what have you. Maximize value as you perceive it to be once you've done your pre-season research each year, and draft to maximize the current season team's value while keeping an eye out for your future, just a balancing act.