Pretty much reflecting what everyone else is saying. It's mostly about making sure your fish has enough strength to make it through the breeding process and time without food, and hopefully prevent the parents from eating the eggs/ fry.
Some of us are much more liberal with our normal feedings that we feel comfortable just pulling them to breed at any time. Some of the fish i bred and sold were making spawns of their own inside of a week of me shipping them with no ill effects. Those fish were without food for 2 days prior to shipping and three days in transit :X
Basically it's a judgement call, but unless you know for sure, two weeks is a good assurance for the best possible result.