Good portfolio management question.
I believe in meritocracy. If a business intrinsicaly perform than the others, it's prospects still look good and the price is fair, I prefer to keep them rather than sell them.
You can compare that with horses. If a horse run faster than the others and don't need a lot of food, you should give them a field to run. If a horse don't run, but eat a lot, you should prefer to sell it to somebody else.
Or, for Canadians investors, you can compare that with hockey players. An employer that I had was an ex goalkeeper in the NHL. He used to tell me that when somebody want to put some pucks in the net and he's good at it, you give him ice. When business managers want to prosper and they are good at it, you give them cash.
So, to me, Fairfax is actually the crown jewel in my portfolio and it's still fairly cheap, so instead of selling them, I keep buying some. Fairfax weigh for 35% AT COST in my portfolio. I'll try to keep that percentage, unless I find a better business to own (unlikely), it's long term prospects are deteriorate or the price become too expensive.
Cheers!