You sign free agents when you're ready to compete at a position of need.
Flyers will have Frost, Couts, Luchanko at center, Michkov, TK, Tippett, Farabee, Foerster, Brink, Cates at wing.
York, Sanheim, Bonk, Drysdale on D.
They also have 5 picks next summer that will probably be in the top 40 plus their own 2nd, so they should probably land 3 more starter caliber players (they can trade up and target players).
And they have to reserve cap room to sign their own players.
Given they're paying Sanheim, Couts and TK $22M for 6 more years, and may need to give Michkov a big contract in 3 years, plus extend a number of other players, how much cap room will be available for a "name" free agent.