I get the feeling, absolutely. But in the end, even with the sped-up progression, every level lasts at least an adventuring day. I think what you're supposed to do around that time is to add much more downtime between each adventure. That way, your high-level PCs still spend a lot of time in-game time at each level, but they tend to level up following short, meaningful excursions. It has some superhero logic to it (unsurprisingly): The Avengers probably chill in their mansion or go on small solo quests most of the time, and then come together every now and again for the big team-up, and then disband until the next big threat rears its head. I feel like the game speeding up after Level 11 can support that playstyle, provided that you find an excuse to increase the downtime between each adventure. What I had done my last high-level game was making a set amount of downtime required after a level up, and the amount of time increased between tiers. So the party may need to spend only one week to go from Level 3 to 4, but they might spend 2 months in downtime from Level 15 to 16.