Anyway, I think the point Dreak is making is that even if it isn't technically in the rules, there is a level of courtesy towards fellow GMs that is appreciated.
Just like technically, you don't ever have to leave a list if your pick is up very soon and you'll be away. But you really should leave a list if at all possible. You can technically sit here for every hour of your clock (once the clock starts) going "nah nah nah, my time, I'll pick exactly 1 minute before my time is up." But you probably shouldn't do that.
Anyway, there is nothing wrong with spending a couple of days trying to trade your pick before the clock officially starts, but it would be nice to get this started sooner rather than later - if for no other reason, then we can all start arguing about the merits of each selection, which is what we are all here to do, not snipe about minor rules.