I weigh pretty much daily, in the morning.
I spent my teens and early 20's yo-yo'ing between around 110 to my high of 175 even though I was very physically active mostly biking - too many burgers and beer I guess. Finally in 95-96 I changed the way I ate and have kept my weight between 125 and 135 since - two 50-pound gain pregnancies aside.

I lost all 50 pounds in 6 weeks with my first. Just lots of nursing...I was eating tons and not exercising because of some pretty severe tears. But I'd run all through that pregnancy so I was in pretty good shape overall. With my second I started WW at 6wpp as I still had 30 pounds to loose, 6w before I needed to return to work and two pairs of pants that fit - one with a hole in the butt.

Anyway, even though its been over 10 years at a healthy weight I still get a little paranoid about gaining. Weighing myself helps me remain mentally in check.