In another thread, Smon wrote that he runs 5e with Long Rests on a weekly timer.
1. Doesn't that drastically alter some classes capabilities? The whole Short-Rest/Long-Rest issue?
2. Do you "speed up" any class abilities to account for this?
For anyone who runs a Really Long Rest , how does that affect gameplay that you've noticed?
1. It can, yes, depending on the party composition. A bard must be vigilant with his Inspiration uses if there's a high chance of multiple encounters per day, while a fighter doesn't have to worry as much. The biggest offender (especially at later levels) IMO is the Moon Druid because Wild Shape is an ability that, especially in traditional exploration and random encounter scenarios, is just is leagues above many other class abilities and having it reset after Short and Long Rests introduces potential for power balance issues.
2. In a way, yes. I'm running a weekly game with a party consisting of: Bard 8, Bard 6/Warlock 2, Rogue 8, Druid 8, Fighter 8 and Ranger 7/Fighter 1. We use a modified version of the travel rules from Adventures in Middle-earth, which means that Long Rests aren't generally viable in the wilderness unless the party finds (and unlocks) a safe heaven/sanctum of some sorts. Now, this can become a huge deterrent against long expeditions since spellcasters will just run dry fast - Adventures in Middle-earth has unique classes and no traditional D&D spellcasting, so it's not such a huge problem in that game - especially at low levels. To mitigate this problem, I added that all spellcasters can decide if they want to use Hit Dice during a Short Rest or regain a single spell slot that is half of the highest spell level they can cast (min. 1). By now the characters are high enough in level that they don't really need that option anymore, but it really helped our game early on and the conditioning of 'Don't Waste Resources!' is still having an impact on the game, which I rather enjoy.
As to the impact of Really Long Rests, we also use a downtime system close to the one from Unearthed Arcana. Players can pursue projects during any downtime of sufficient lengths, do research, learn new languages, and so on. Of course, the world doesn't stop in the meantime and more than once the group had to decide if they can really afford to give the bad guys an advantage by taking a vacation. I like that it adds so much to the political aspect of the game (the party also owns property and is building a base of operation, which of course also feeds into this). Right now for example the party has defeated their biggest long-term opponent in a climactic battle and can do a 'real' downtime for the first time in (in-game) months, which has some folks pretty excited.