Xethreau
Josh Gentry - Author, Wanderer
Ironically, although XP systems create a facade of fairness, 5e XP (and that of systems which inherit it like A5e) doesn't offer much of a compelling standard against which to measure milestones. That is to say, even the crapiest and most unfair milestone leveling standards are likely more rigorous of expectations than standard 5e XP leveling.the problem with milestones is the design of the game and it's increasing difficulty for the DM to juggle things at High level is that Milestones enable lazy DM's who want to play something epic like save the world but don't want to deal with High level to just ignore leveling. And even when the DM is being fair about the Milestones it can sometimes appear to be unfair. That's why people don't like Milestones it just appears unfair from the surface and most DM's don't put effort into making sure everyone knows that it is being done fairly. And far too many just don't use it fairly and use it as a way to avoid high level without restarting thier game, or getting table buy in to quit leveling.
Per my previous analysis, high level play has a surprisingly low number of encounters per level. We would expect that each level would require the party to expend their daily resources several times over to level up; we call the expendeture of all one's daily resources an "adventuring day." For high-powered characters with a lot of resources, that's a lot of long adventuring days---a lot of encounters! However, using A5e's Encounter Points Per Day system, we can see that at high level you don't need to spend all your daily resources in order to reach the next level: starting at 11th level, most characters can reach the next level even before completing one full adventuring day! By that point you've moved right past MCU flavor and stright into Gurren Lagann.
IMO that is not expected or desired. In that case, it would seem to me that "just do whatever" would be far better advice than following the RAW.
(And in case anybody was wondering, this is the reason why I say resource management doesn't matter in 5e. There is rarely a reason past 3rd level not to go full blast; at 11th level it is practically law. But maybe people like it that way.)