How many classes can I reasonably keep at quest level through Endwalker and Dawntrail?

At some point in my questing journey I ended up with an egregiously overleveled warrior, then slowly started catching other jobs up.

As I've been playing through Shadowbringers I'm on the level 78 quests. I've got six classes I really like at 80 and the rest at 77. I feel like the leveling is slowing down.

Assuming I do all daily duty roulettes, how many classes could I keep around main quest level? I'm trying to figure out what I main for the rest of the game.

At 80 I've got (and would like to rotate through):

  • Warrior
  • Sage
  • Reaper
  • Red Mage
  • Picto
  • Viper

Any chance I can keep these six going through the next two expansions?