For me, burnout happens when there is nothing "new" for me at the moment - when I have pretty much "mastered" the mechanics and there is nothing "new" to be expected, I hit burnout. Essentially, I have reduced the game from being a fun, immersive experience, into being numbers and patterns on the keyboard.
So, let's take Rome: Total War as an example. Start the game for the first time, OOH Romans! Build some armies, fight some battles, take some cities. Immersive AF, this is fun! Play more and more! Learn the mechanics and use your human brain to build effective armies. Start learning the limitations of the AI. Take another city, fight another battle. AI makes no sense. Has one province against your 25 provinces. No surrender, no ceasefire. It's hell in a handbasket or nothing. Meet AI armies that are clearly the result of a poorly coded strategic AI, that consist of 20 units of heavy cavalry, or worse, 20 units of seige engines. If the AI wasn't so busy building all of that heavy cavalry he could have built some real contender armies instead. AI is threatening my territory. I will run one velite just our of reach and into his territory in order to call his 50,000 man army off and throw his whole "campaign" into turmoil. AI has an army of 4 bloodied light infantry just sitting there, waiting for the slaughter... Army is worth 200-300 Gold, max, army wants 12,000 Gold to defect. AI makes peace with you because you outnumber him 20:1. Next turn, AI blockades one of your ports. Tactical AI has no concept of flanking, no concept of cohesion. It's like ants when you kick over their hill and they run panicking in every direction. Eventually, you're pretty confident that anything better than 2:3 odds and you'll be able to win.
Eventually, you just burn out on it. You've gotten past the immersive, fun battles and conquest, and it all has just boiled down to by-the-numbers tedium. That's when it's time to put it down for a while. Eventually, you might read a book or see a movie about Rome, or just think fondly of the game, and go back to it. Have fun with it again, and play it for what it is. But you'll hit burnout again.
That's video games.
I also suspect that's why PvPers enjoy what they do so much - I played a civil war game with my dad
years ago. He kept and entire division of mine pinned down by running two regiments in circles, in and out of my line of sight. Next thing I knew, POW! Right in the kisser
