Pretty much you can boil it down to a basic guide on predicting when something will be released. It is not 100% applicable for all situations, but it will save you from asking every release day if X is going to be released. Basically, from my observations - a render is released of the finished model, then you'll see some teaser shots in the modeler/scripters personal routes, followed by a cab render being released, and finally the item starts appearing in beta tester's screenshots. The middle two aren't always there or in that order, but if you haven't seen many recent updates or beta testers showing off the model then you can pretty much guarantee that the item is still a few months out and you can stop worrying about asking when it is coming. Other things never get previewed before being released, those being my favorite items, and they just pop up in the release thread with great fanfare. Now stop stressing about P42s and go buy stuff that is on sale.