I'd be worried about three centers in their mid-30's.
I would too if their names were larry, curly, and moe
but no worries about Bergeron anytime soon... will let you know in a few years maybe that changes... wont be changing this year
krejci had another ace playoffs at times last year... had his best regular season... he might be a bit shy of what you want for 7.25 mill but I dont think thats because of age. he is what he has always been
and as for mikko... I think theres a damn good chance he welcomes the opportunity to get out of minny and that depressing style he was forced to play his entire career. also some relief not to be the 'number 1 guy.'
ive seen many cases of guys going to teams like detroit in past decades to wind down their all star careers playing roles on 3rd/4th lines and being a huge advantage to those cup caliber teams.
honestly ive been wishing for boston to have the ability to do this for years... was so excited when we got recchi for exactly this reason. old gray tooth hof guys like to win on their way out of the league... and they can teach the kids around them some of the secrets how to win.
the value is greater in grizzled guys that have winning pedigree, than it is in kids who have struggled to ever get their acts together wherever they played before