BTW, the resource recovery balance in 5e is my biggest gripe about an otherwise fine game. I greatly prefer how 13th Age does it. (If you've heard me give this spiel you can tune out now.)
13th Age is a d20 by lead designers of 3rd & 4e that came out before 5e but shares a lot of it's philosophy. But the one thing I love is that they divorce the in-game mechanism of resting from the resource recovery mechanic. At their basics, they have at-will, per-encounter, and ones that recover on a full-heal-up. But a full heal-up happens every four encounters, not attached to an in-game event.
A three week trip across the savanna with four encounters? Full heal-up at the end. A day adventuring with four encounters? The same. Two days of two encounters each? Full heal up after the second day. A dungeon delver with four encounters in the morning and four more in the afternoon? That's a recovery at lunch and another at night.
The DM can make it less if they are throwing harder encounters, and the party can always "force" a rest, but they take a campaign set-back in return. Perhaps the vampires turned a pair of the villagers they made off with, or the cult completed the first stage of their ritual and now have a minor demon guarding them.
It's such a sacred cow, but it works so much better. Adventures go at whatever pace makes sense, and the mechanics still balance out.
To yoink it for D&D, something like a short rest every other encounter and a long rest every six.