People might be impatient because they don't remember back to 2003 and 2004. In those back to back years, they drafted their future #1A/#1B centers for the long term. Since then, only Spooner in 2010 with something like 30-40 NHL games, has been drafted by and played more games at center for the Bruins than JFK's 14.
Estimating their games at center, it goes about 950 games, 780 games, 30 games, 13 games among those drafted, developed, and deployed as centers as Bruins players. (obviously Seguin has played 420 games for Dallas at C but was not used there but for a couple games as a Bruin)
If he stays with the Bruins, JFK should pass Spooner's games-at-center number around the beginning of March: 11 years between drafting and developing centers. We can forget during that time how much Krejci struggled his first 2 years in the NHL or the Dave Lewis era with a -28 Bergeron as your #2C.