Ramblings as I am wondering about the duration of fights in a session and the expected values of XP accrued over an Adventuring Day.
If groups get the expected XP per Adventuring Day, they go from level 1 to 20 in 34 adventuring days. If they are expected to take a Long Rest after each adventuring day, that would first mean that they are expected to enjoy very few long rests over their whole carreer. I am surprised they decided to link "long rest" with a "day" when it seems strange that the PCs would spend so few days adventuring over their carreer. The variant rules exist to make these "adventuring days" occurr over longer period to accomodate different paces, but I am surprised that the "day" was kept as the standard nonetheless.
The second thing I notice is that the first 3 levels are quick (basically, you level at the end of each day), then there is a lull from level 4 to 10 where PCs are spending 2,23 days at each level, then leveling resumes at a brisker pace (1,58 day per level). So nearly half (156/333th) of the PC career will be spend between level 4 and 10. After this range, strangely, spellcasters for example are expected to spend less than 2 adventuring days at this level ; if you're throwing more XP than the expected, they might even not have a single long rest until they level up, so a wizard could expect not to refresh his spells before reaching the next level, and be quite certain he won't refresh them more than once. I am not sure it's the default assumption a player makes when considering his strategy, especially as at higher level, you need to increase the XP budget to make encounters challenging.
What strikes me with the idea that a session could conclude with a long rest is that PC would expect to level every other session at most. I am not sure it is, also, the behaviour observed when people are using story award XP, for example.
Finally, when I read that the idea was to have 10-minutes fight, so 6-8 encounters takes less than half of a 4h session... I am envious of the other players. It usually takes a few minutes to describe the scene of the fight, establish positions and get ready to run the fight... Based on a 3 round average, that's 2 minutes per round for 3-5 PCs and the DM running the monsters. As it often recommanded to avoid solo encounter because of the action economy, even as a prepared DM with a pre-planned strategy for monsters, I am not sure how can each action be resolved with a few seconds per character per round, especially when the fight is designed to encourage tactical thinking. Are combat supposed to be shorter (in rounds and descriptions) than what I usually run? I am not a critical role watcher, but I checked a fight on their show (the midnight chase) that starts with a fight going on... Their experience is more typical of what happens at my table.
From 8:50 to 10:50 they basically roll initiative.
From 10:50 to 12:25, two zombies move.
From 12:25 to 26:05, the PCs act.
From 26:05 to 36:50, that's the second round and consequences of the fight.
That's roughly half an hour where 6 level 2 PCs fight 2 zombies... Not exactly a high level fight and still, it's quite long to play. I'd worry that a 6 to 8 fights would take all the session...