How Fast Should Characters Level Up?

The latest Rampant Coyote blog post deals with leveling up speed, a pacing problem that pretty much every single RPG developer has to solve, and that often prompts large debates between supporters of a slower, steeper leveling curve, and fans of the faster, more even leveling curve that's become popular with RPGs in the last 5 or so years.

I'm going to be a bit generous with the quoting, but I feel that's necessary to understand the context:
Class / Level based systems of which Dungeons & Dragons was the role-model were generally slower, with intermediate gains usually in the form of improved equipment. But then you got all of your gains as one package of bonuses, which felt great. In skill-based systems, the incremental improvements were not as noticeable, but suddenly being able to cast 3rd level spells in D&D was huge on top of extra hit points, better chances of hitting, better saving throws, and more spells overall. Instead of a constant slope, you had a staircase, where each step felt like a significant increase. Unless you were playing a fighter, I guess.

But in earlier editions of D&D, those levels (if the DM was playing by the rules *) came pretty quickly early on, but came progressively slower. It was not uncommon to hit 2nd level after a single adventure, but going from 7th to 8th level might take months of weekly sessions. One might argue that this was really too slow and would make characters feel stale and drag the game, and that would not be entirely incorrect. However, up through the 1st edition of Advanced D&D there was something of a (soft cap) around 9th level (closer to 6th level in the original), after which non-spellcasting class progression became really kind of meaningless. So around 7th or 8th level you were really entering the (end game) area, and at that point progression really became more about acquisition of equipment (and sometimes followers, and eventually even castles).

...

But most CRPGs nowadays tend to keep progression at a pretty steady, rapid pace, slowing gradually. For MMOs, I'm sure teams have it down to a mathematical abstraction of something like a level per 20 hours of average, active play or something along those lines. For action-RPGs, it seems like it averages closer to a level every hour or two. My own game, Frayed Knights: The Skull of S'makh-Daon, slowed things down a little bit with only around 10 levels of progression for an approximately 30 hour game.

Obviously, there's no magic number for an (optimal) progression rate. There are way too many variables. The player should be having a good time throughout the game, and whether that's because of treasure hunting, achieving new levels, having a blast running through levels or being riveted to the plot or any / all of the above, is immaterial. But it does seem that there's an expectation of a more rapid pace of leveling in modern CRPGs than there was in previous eras. Then again, people generally have less patience for the length of the older games, but I hesitate to make that any kind of blanket statement considering the length of some of my modern favorites.