I see a lot of people here boil their butter for hours. I used to do it that way too, but then I tried 30 minutes and I don't notice any difference. I have been boiling for only 30 minutes ever since. I plan to try 15 minutes to see if that is just as good.
The main problem with the extra long cooking time is that it keeps the house stinky longer. Make no mistake, this stuff is very stinky. That means keeping the windows open for a long time and no air conditioning. That can be a problem in the summer.