TVE/Tom...
Brussels sprouts really take quite a long time to mature, some varieties nearly 120 days or so. As for picking off the lower leaves, I'd pick them off only when you start harvesting the lowest "sprouts". Those lower leaves will be showing signs of yellowing at that point anyway.
And, as you probably already know, feed them a nice high-nitrogen food (blood meal, cottonseed meal) or a good foliar fertilizer every month if not every 3 weeks.
Hope this helps.
Shoe
