I really don't disagree with anything you guys are saying, my oc was more geared to the point OR made earlier.
Ideally in an extension you're overpaying for a guy during the arb years, especially pre-arb years (which doesn't apply here) but you're saving money in later years.
Given the Sox payroll status, and seemingly staying under this year, it's 100% logical and the right move to make to use that cap space THIS year for extensions. You can make them, stay under the cap and possibly be in a better position 3-5 years down the line because of this.