I use under 6 long rest for EA. From the beginning, you can go until L3 and the Druid Grove and Owlbear.

Rest after Blighted Village + Wood Woads + Redcaps + Hag Lair.

Rest after Gnolls, Tyr Toll Bridge Brigade, Waukeen's, Githyanki.

Rest after Goblin Camp is cleared entirely.

One rest in half of Underdark.