Level Limits - Defined by the Story

I was searching through old posts today, looking up what now seem like ancient and long-forgotten details about an event that took place twelve years ago in my play-by-post campaign and stumbled across an article about level limits in AD&D. This concept has largely been abandoned over the intervening decades since the creation of Dungeons & Dragons with 5e essentially capping out at 20th level for everyone but it got me to thinking about the story my players are currently engaged in.

In earlier editions of the game, it was commonly accepted that the time of elves and dwarves, et al has passed with them reaching their "maximum potential" somewhere between 8th and 11th level. Humanity is the mover and shaker of the world now but it seems to me, and always has, that an elf with a lifespan of hundreds of years is going to amass more experience and have more time to hone his skills than any human.  The same can be said for dwarves and gnomes who also can expect to live to over 300 years.  Does this mean that demihumans will dominate whatever campaign setting your game is set it?  No. Because they have so much time on their hands, it is not unreasonable to assume that elves, dwarves and gnomes would be terrible procrastinators.  Plus, how likely is it that they would have the same interests after decades of adventuring? Not very. They're going to want to experiment with life, try new things, settle down and raise a family and for an elf, the 18 years a human has to wait to get their kid out of the house stretches out to more than a century. Plus, they're going to want to enjoy what they've worked for. In our very own group, Kysek took 10 years to live off his savings and party pretty much constantly. It wasn't until he ran out of ready coin that he took to the road in search of adventure once more.

Story Reasons, Not Game Rules should set the only limit on advancement for any character. 

The "Labyrinth of Madness" is a 2nd ed module that has no upper limit on the level for the adventurers participating in it and "The Throne of Bloodstone" is for characters from 18th to 100th (yes, 100th) level. I plan on our lowest level party members (or at least those who participate regularly) being at least 25th level and for the higher level guys pushing or exceeding 40th or higher when we finally reach the grand finale of our tale.

And then, the story will really take off.