Wright has picked a good time to renegotiate a new contract, coming off his best season in four years, and one of the three best seasons of his nine-year career.
We - fans, analysts - like to think of baseball players' careers as following a nice smooth progression, where a guy might gets gradually better through his early-mid 20s, peaking near 27 or 28, and then declining gently thereafter, after all it makes analysis easier. Of course, it doesn't work like that in individual cases. It might be true in the aggregate, but it is not hard to cherry-pick unusual career paths. Jason Bay did not age gracefully. Mike Schmidt, who just so happens to play David Wright's position, was an excellent player deep into his 30s, winning an MVP at age 36.
If David Wright is a 5+ win player for most of his contract, he would be well worth any of the range of potential outcomes from ~$16-20 million annually, that have been kicked around the press. Not to put too fine a point on it, but Wright has been that player once in the last four years and three times in the last six.
One of the areas of volatility in Wright's performance has been defensive, bouncing from -1.4 dWAR in 2010 to 2.1 dWAR in 2012, a swing of roughly 35 runs over full seasons of action.
He has been a more consistent hitter, varying between very good and elite (with the exception of his injury marred 2011 season).
Where the WAR graph of David Wright's career resembled a roller coaster, his offensive production merely looks like a bumpy road. It is this, Wright's relatively more consistent production offensively, that make a six, seven or even eight-year contract less scary.