Since I don't have an umlimited number of crew, and I prefer to have everyone fresh for the morning, I don't have a steadfast policy on anchor watches.
I always let the weather conditions, bottom conditions, familiarity with the anchorage, and a number of other factors determine whether I will post a watch. We spend alot of time in the Bahamas in anchorages that I know like the back of my hand. In these cases I rarely post a watch and prefer to get up every hour or two in order to check on things. Sometimes that just entails opening one eye long enough to check the instruments in my cabin, and sometimes it means walking the decks (usually in my skivvies as I have a private entrance from the main deck).
If I'm not familiar with an anchorage or am uncertain of the weather, I'll spend the night in the bridge and catch a few winks when I can.
If the weather is down-right going to be bad, I'll post a watch and do rotations with deck crew and engineer.
On one boat I had my cabin directly behind the bridge and could see one of the radars from my cabin. I would then lock all the pilothouse doors and sleep with my cabin door open. That was a nice piece of mind.
That's my 2 cents.