From table top to online, I don’t know of many people in my personal circles that didn’t create some sort of roadmap that they were hoping for their character. In the forms of Race, Class(s), Feats / Talents, Skills / Prof well in advance. The room for growth was watching the character make their way to that end goal, even if it was one story instead of one level at a time.
This character is only 60 and with each level I got to watch her grow. Growth doesn’t have to be earth shattering result after earth shattering result. Even Rome wasn’t built in a day.
People have to realize that there will come a point where the overall story is going to end. No amount of mind numbing grinding is going to change that. You will have those that are diehard players and will blow though whatever content you create. Oh well, it’s their issue if they are just blowing through it.
You create enough content where you are looking at the average player and seeing how much they are playing on average and you figure out how long you wish for that expansion to last based on that average.
Some people will do it faster, and some will do it slower. It’s the nature of the beast.
It doesn’t have to be, but gear can be a good incentive. Just as cosmetic and toys and the like can also be good incentives. It all depends on how creative the people are wanting to be when they design the game.
Having a lack of content and limiting that content behind paywalls / energy bars and the like is a terrible design.