Draw weight is somewhat variable, based on temperature and humidity. How much that varies largely on where you keep your bows and the level of moisture resistance the finish has. If you keep your bow in your climate controlled house, there may be little, if any draw weight difference through the seasons. And if you've used a good finish, you can take it out and shoot in the rain, probably without any temporary weight loss. But, if kept in the garage, and lacking a good moisture barrier, the draw weight may bob up and down several pounds as conditions change. Draw weight is variable too, on immediate useage. A freshly braced bow can pull 1 or 2# more than after shooting a couple dozen arrows. (But not always.) The key is measuring the weight against the relative conditions. I prefer to weigh bows after they've been stored indoors (never a problem) and have been braced and shot at least several times.
How much weight the bow looses during shoot-in depends largely on how much you've exercised the bow during construction. If you've drawn it a few dozen times along each increment of length after every round of wood removal, and particularly if you've allowed the bow to remain braced at full draw once or twice or more overnight near final tiller, then by the time you shoot it in with a couple of hundred arrows, you'll loose virtually no weight. The less you've exercised it, on the other hand, the more weight you stand to loose and the bigger the chance of the tiller changing during shoot in.
