HI - I followed the Gina books for my first boy who is now 3, and am doing the same for my second boy, now 3 months old. Don't listen to the knockers, if you feel her routines are working for you, stick with it. I don't follow her advice to the letter. Each baby is different and you have to work out how it works for you and your bub.Our second baby at 9 weeks, also struggled to stay awake longer than an hour and a half, so you just have to adjust the routines slightly. Now at 3 months according to Gina, he should be sleeping no more than 3 hours in the day, but he sleeps about 3 1/2 and still sleeps from 6:30pm til having to wake him at 7am, with a sleepy feed at 10pm. He has always been a sleepy baby.
After following Gina's routines we have a 3 year old who sleeps in a big bed and does not get out of bed in the morning until we come to him, and we have a 3 month old who self settles and has to be woken at almost every sleep.
I'm not saying there won't be hitches, but I strongly believe persistance pays off. What works for you and makes you and baby happy is the best way to go, and Gina's books aren't for every one.