I've had 2 bottom brackets go out on me. They clanked randomly. I think that was the bearings? They told me I was eating through the bottom brackets because a) I had the cheapest components on that bike and b) I pull a trailer with heavy stuff. Also winter weather, and just lots of miles. When I got my "new" bike (3 yrs now) they told me not to get the lowest end because I would need better components--such as the bottom bracket.

They're not expensive and if you replace them before they break inside the bike it's not hard to do. One of mine broke inside the bike and we spent hours chipping out the pieces without damaging the threads!