we started, cold turkey, yesterday [dd's 3 months 1 week+]
I was having terrible problems with putting her to sleep, she didn't feed well [not at all hungry in the morning, starving in the evening, waking up a lot at night], and suddenly I realized she can easily handle 2 hrs A time. so I thought there was no point in changing her routine gradually.
some time before I was wondering if she was ready for 4 or 3,5 hrs EASY but just couldn't do anything as she started teething [we had 3 days of a real nightmare!] and had some tummy problems the same time.
and now, I must tell you, she's so much happier already! and today she slept until 7:15
real shock to me! with a DF at 11pm and more a snack than a feed at 3:30.
I hope it will continue working for us.
good luck to you !!!