I'll preface this with the fact that I didn't bother to read beyond this post...
I voted "nothing," because I don't think it's a problem. The DM already has absolute control over this phenomenon: he or she controls the number of encounters, the amount of down-time between encounters, the length of travel and availability of safe resting locations, time constraints, amount (or lack) of additional resources, etc.
By tweaking any of these variables, the DM can set the length of "the game workday" to anything he or she needs it to be to fit the pace and feel of the story.
Not broke, don't fix.
I voted "nothing" also. This isn't a problem unless the DM makes it/allows it be a problem.
Yes, you COULD have mechanics to discourage it or ADVICE to discourage it...but it all boils down to the DM. Will they take the advice? Will they USE the mechanics presented? Yes or no...it's down to the DM.
If the DM discourages it, the players will fall in line. Or...rather...not "fall in line" but
learn from the experience!
Can I [the wizard] nova all of my spells (or any other class' "Dailies" or what have you) on a single encounter in the first hour of the adventure day...and look really cool doing it? Yes. Yes you can...and then, when other things happen during the day...you have NO RIGHT to whine or kvetch that you have "nothing to do." That's not the "system's" fault...that's the player's.
YOUR character. YOUR resources...YOUR call. You made a bad choice...perhaps...or perhaps not...but, if so, you know better for the next [in game] day. And if you do and convince everyone to "rest" again...the DM is under no compulsion to "hold" the goings-on of the game world.
Yes. I know I come at the game from a differnt place than many of you...but the fact of the matter is, particularly for 5e, it is [or should be] up to the DM where the "work day" ends. If they want to allow you a rest every hour of the day...that's on them...and will make a better or worse experience for you as a player.
The advice and/or mechanics should not or, I believe,
can not dictate that for you.
--SD