I'm about 25 years into my first CK2 game.
I of course chose Harald Hardråde, who started out fighting a futile war of attrition in England for a few years, eventually packing his bags for home and offering white peace. He passed away in bed over two decades later at the age of 75, presumably with a smile on his mouth, while his pregnant 17 year-old wife (and sister of the scottish king) mourned her loss. Not for long though.
After Hardråde's death, his son and designated heir Magnus was elected king of the realm. I hadn't paid proper attention, so this by now middle-aged duke had acquired a number of bad traits, with most skills in the low single digits. Also mostly disliked by the vassals. Also hated by his own wife. Also his oldest son, who had been the ward of Hardråde and shown such promise, had gone ahead and married the closest blood-relative he could find that wasn't a sibling (the daughter of Prince Olaf, his uncle).
So what's a cruel, arbitrary king to do? Time to explore the intrigue screen, which I had ignored throughout most of Hardråde's rule.
First plot: arrange an accident for the daughter-in-law to keep the gene-pool fresh. Unfortunately there was a son before the plot could succeed.
Second plot: arrange an accident for said grandson.
Third plot: do away with the grumpy old queen.
Fourth "plot": have the king marry his ex-stepmother and by now mother of his half-sister. Would be a shame to let her skills go to waste (diplomacy and learning at 20+, the rest except intrigue at 13+).
Not long after the wedding, the king decides to hang out with the steward's wife, so
Fifth plot: have the king's mistress killed.
Then spent a lot of cash improving relations with important nobility and optimizing the demesne. The king might be dumb and fat, but he'd built up a nice fortune.
Reasonably productive first four months of rule I guess.
Edit: sheesh, my english is horrible sometimes.