Every time I see people mentioning cloning their Macs (the most recently post about it was by Gruber I find the hours they choose a bit odd.
Like Gruber, most of the people clone during the night. What I find odd about that is that during the night your Mac should be turned off.
I prefer to do my cloning during my lunch break. The laptop is usually in my place of work, where I keep my main clone disk (the second is at home), its usually turned on (I'm working right?) and the time it takes to smart update matches the time I take to have lunch and play a bit with the kids.
It feels natural to use that off-period during the day than the night, but maybe I'm just odd that way.