The leaves are making sugars to build the bulbs up for next year. I think if you cut the leaves off right away, it will make for less healthy bulbs.
Susan

I generally let the foliage go for six weeks minimum, and have good results as far as blooming the next year. If you can stand it, leave it longer. Many people tie the daffodil foliage up into bunches to make it less floppy, and this doesn't seem to hurt the bulbs. The other thing you can do is intersperse other perennials into your bulb plantings so that as the bulb foliage gets ratty, it is hidden by the emerging foliage of the companion plants.

- Steve

Actually, braiding or tying the foliage is not good for the bulb; as the hidden parts do not get into photosynthesis as well as the exposed parts do. Wait at least six weeks before cutting the foliage and if you can, wait until it all turns brown. If it is too hard to look at, consider planting annuals on top to help hide the brown foliage.

I can agree six weeks is about right. As soon as the bloom is spent the flower should be cut off, do not remove the flower stem only the flower. This will prevent the formation of seeds which uses energy that would otherwise be put into next years flower. Al

I don't cut back the stems until they go brown, and am generally rewarded the following year (this year some of my tulips and daffodils look sad, probably because of a late frost). I "hide" the stems by planting my bulbs in with my perennials as Steve suggested; daylilies work great, as they come up at just the right time. And I agree with not braiding or tying up the foliage. I was very disappointed to see this suggestion recently in my favorite gardening magazine. Al-thanks for suggesting cutting away the flowers, I've never done that and it certainly makes sense.
Vivian