I’ve been running RPGs and working as a teacher since 2010. These two roles have, ironically, always been very similar to one another. Over that time I’ve learnt plent of tips and tricks for keeping a players attention. But out of everything else though, the number one thing I’ve learnt from them both is the ’40 minute rule.’

Generally speaking, people can only keep their attention on the same thing for 40 minutes at a time before they begin to feel bored. Whether its reading a book, painting a miniatures, or creating a character. All of these activities begin to feel like a chore to most people if they are doing the same thing for a full 40 minutes at a time. Thus, I put a simple guiding line over any event or encounter in my games. If it will take more than 40 minutes it needs to be changed.

Now, changing the encounter does not mean it has to be shorter. An epic 3 hour battle is still something that a lot of players can have fun with. Instead the conditions of the encounter have to change. Multiple phases to a boss fight (The mythic creatures in D&D 5e are a straight forward example of this with the creature having multiple health bars and new actions available to it after it first drops to 0 HP. ) Changing the objectives of the encounter such as having the fight start out as a simple foot chase through the streets, escalating into a daring fight, and finishing with an escape from the town guard. Or it can even be as simple as having a dynamic environment for the encounter like moving ships or portals spawning new demons every few rounds.

Keep it simple and keep it fresh.