Hi Nilly,
Wow, we are in the same boat! I posted this question elsewhere already, but thought I'd chime in on your post as well. I have a one week old boy, and a 20 month old daughter. Maybe we can help each other out along the way!!! I've found that anywhere from 30-60 minutes is what my lo can tolerate, but 45 minutes is a pretty good average. Sometimes after waking up from a long and deep nap he can do a little longer, and other times, it's like I can't really even keep him up at all before he slips back asleep again. But I think really encouraging at least a little awake time has been helpful, because our lo is sleeping pretty good at night now. I didn't discover the baby whisperer until my older daughter was about 3 months old, so doing this with a newborn is new to me. But things went so well with my 20 month old, and still is, that I am determined to do it again with this baby...
Anyway, congrats on your new lo...
photomommee