The Red Sox have not been in a rush with Lester. Most sources said that discussions would begin in Spring Training. It gives the team a chance to see what shape and health Lester is in after his 240 IP season. Ben prioritized the offseason on new acquisitions. Lester really wants to come back, and there are a good number of reasons that make him desirable to the Red Sox.
Playoff history, durability, consistency, numbers, relationship with Farrell and the rest of the pitching staff, team chemistry, the composure to play at Fenway. He's always the first one to report to Spring Training and wants to be in Boston. People were skeptical when reports came out that Lester wasn't involved in Beergate, but honestly if reports came out saying he wasn't part of Beergate -- even if they were lies-- it means that someone upstairs probably likes him.
The team just gained 13 million to Dempster, they're gaining 30ish million a year more on Peavy and Lackey next year. Homer Bailey is off the market, James Shields is 3 years older than Lester, and Masterson isn't in the same league.
Lester's contract extension is inevitable and it makes sense in every single possible way. It will happen.