Most of the time I go for 1 at a time...
Or 3!
3 for saving on the shipping, if I'm sure I'll buy these watches soon, why wait... The risk? well, I don't think it really is that big... or that much reduced going from 1 package of 3 to 3 packages of 1... Less loss at each time (1/3) but higher probability (3x) so that doesn't count.
The point in going 1 at a time, is mostly to force myself not to buy too many watches! However, I'm going to order 3 watches soon... Each one from a different place and of a different type (one rep, one gen, one homage... ). But that's rare.