IME, it really depends on the child. We do it every so often (Montreal QC to BC and back, so three hours again) and we just switch them to the local time. When we arrive, they are up late in real time so we try to make sure they nap in transit, and really well the next day. Same for the way back. It takes a few days to adjust and DD does fine. It is our first trip since DS was a baby this summer, and I am curious how he will handle it. i think he might be more tired that she ever was. I have friends as well who move BT incrementally in the weeks before but that has never worked for us, since we aren't able to move waking back or no-one would get to work on time. Also, they both resist a BT change and just stay awake until the 'right' BT.