sorry i have hot replied- i was not notified by bw website!!
the book does not say any age to start to implement, any age is good (personally, i think that the earlier, the easier.... as it's taking some time w/ my 8 1/2 mo..)
as to g.k. and lkaiser- maybe they aren't rested enough after only a 30 min nap? therefore they aren't sleeping as well? mine doesn't usually function very well after only 30 min, and i usually have to put her back to sleep once she wakes up-- i was doing this before i found the book-- i would go in as soon as she cried, and put her on the breast (haven't broken the food/sleep association yet so i'm not too concerned about that at moment..) and once she is drowsy, i put her on my shoulder where she starts to drift off and then back into bed for her second half of her nap. do your little ones wake up rested and happy or crying? if they are crying, try Elizabeth Pantley' method of extending naps:
-a very SIMPLE method she has to get the short napper to sleep longer: "...put your baby down for a nap. set a timer or keep your eye onthe time. about 5-10 min BEFORE the usual awakening time, sit outside the bedroom door and listen carefully (using this time to read, knit, fold laundry, pay bills, etc). The minute your baby makes a sound, go in quickly. you'll find him in a sleepy, just-about--to-wake-up state. Use whatever technique helps him fall back to sleep-bf, rocking, or offerin bottle/paci. if you've caught him quickly enough, he sill fall back to sleep. after about a week or so of this intervention, your short napper should be taking a much longer snooze without any help from you..." SOUNDS TOO GOOD TO BE TRUE! however on my first (and only so far) attempt, my munchkin went from 30 min to 1 1/2 hours.... one off? maybe... hope not!
hope this helps- i'm going to post another bit of her book in just a bit- i will put it in another post labeled- PART 2
any questions, i will try to answer!!