Thank you for sharing that. In the lawns forum I harp on the idea of deep infrequent watering as THE way to stop weeds. This is exactly the kind of testamonial I've been looking for. Isn't it funny that you can have your lawn right next to a crabgrass lawn and the crabgrass doesn't encroach? It's all about good management.
What you were doing before, and even moreso your neighbor, is watering to encourage seed germination. Think about what you're supposed to do when you are planting new seed: you water every day, even twice a day, to keep the seed moist. Well, HELLO!!! If you're doing that after the grass is already in, you're encouraging the rest of the seed (weeds) to sprout.
Please don't think I'm picking on you. I sincerely appreciate your writing in.