That's the case with most relievers because they're middling talents whose performance can really fluctuate in short spans, especially with short relief outings. Wood is in the pen because of health, and that's the chief risk in giving him multiple years given his success as a reliever and his stuff. That said, I don't mind letting Wood walk and taking the picks, and I think we could probably even get by in the pen with the odds of Marmol and 2 of Samardzija, Wuertz, and Gaudin having good years(Ceda would be lingering as well if he's still around). I wouldn't feel good about the talent level in the pen though, and would want to add someone like Cruz or Affeldt, at which point you debate if it's simpler and maybe just as efficient to keep Wood around.