I suppose that it depends on what you think the comments are for. If they are for someone else, it makes sense to expand accordingly. If for yourself, write as much as you need to remind yourself of what you were doing (thinking etc.) when you wrote the code in the first place.

Over the years I've noticed that I've become a little bit schizophrenic about documentation. For example, the first thing I do when evaluating someone elses code is to create a copy without comments at all. I'd rather see what the code is doing without being distracted by what the author thought it was doing! On the otherhand, I prefer to code using some form of Literate Programming (see Knuth) whenever I can. I think that this kind of contradiction demonstrates that this is a hard topic!

hsm