When I refer to the 'window', I'm defining it to be the years where your base level talent is of a 97-102 win team. This seems to be what it takes to win these days as the league has become much more top heavy. Yes, the Yankees are likely to win 90 games every year even if they lose Sanchez and/or Judge but LeMahieu, Hicks, Cole and Stanton are all 30+. You have to project some decline from them, and whichever prospects graduate not only have to replace Judge and/or Sanchez's production but also replace the production from the 30+ players, who are all on long term deals. If the CBT limit isn't raised and the ownership is intent on staying at the limit, IMO, your 'window' is done after 2022. If the CBT limit is raised $30-40m then you'll have enough payroll room to top-up the base level talent through FA to replace production from the 30+ players. Like you implied, your farm system is strong enough to continue graduating players.
The Dodgers are way over the limit this year, and assuming of course that they want to reset the tax level once every few years, they won't be able to resign Seager. The rest of their core are also getting expensive (Bellinger) or aging out of their primes (Kershaw, Jansen, Betts). I don't know enough about their farm system to know whether they have enough replacements.