This subject came up in another thread, but I think it deserves its own discussion.

When I was a kid, putting an egg into boiling water for three minutes yielded a perfect soft-boiled egg: firm white and runny yolk. That doesn't work anymore. I find I have to boil the little darlings for 5 1/2 to 6 minutes to get the whites to firm up. And I live at sea level.

What is going on here?

Cheers,
Michael