The answer might surprise you.
During the course of fabricating trusses, on occasion a plate is not completely pressed. As the truss comes out of the finish roller or hydraulic press, the plate sometimes does not get pressed all the way. Sometimes the plate is missed or removed and up plated. In these situations, the plate was never pressed in, so repressing is merely completing the pressing operation. This would count as one press.
Trusses sitting in the weather suffer a phenomenon referred to as plate withdrawal. This happens when the lumber swells and appears to push the connector out. If wet lumber is used to assemble components, this withdrawal can occur as the lumber dries out. According many experts, including Bruce Hoadley’s book, “Understanding Wood,” wood that is wet before pressing will require pressing home after the wood has dried. This second press would count as the first press, since the lumber was expanded prior to pressing. Lumber that becomes wet after pressing unfortunately suffers compression of the wood fibers. As the lumber dries, the plate is backed out, just like a nail will do in a wood deck. The same problem is illustrated by taking a loose ax head and soaking it in the pond to get the head right (see example in photo). It works while the wood is wet, but when it dries the loose head problem is worse.
The problem is the compression. Driving the nail back into the deck secured the deck board, but its withdrawal value will be reduced from the original design value. The same is true with connectors. Once the dry lumber is plated, then wet, and then dried, repressing will not result in the full value of the connector. For this reason, special analysis and consideration must be made when repressing if trusses are built, stored in weather, and exposed to a wetting, drying, wetting cycle.