Last time we had an engine measured and sealed, at SpeedWeek '09, Tom Evans (then the Chief Inspector) told us that the seal would be honored for a year. We didn't have the opportunity to find out if that was a strictly-measured year of 365 days, or might have extended through the following SpeedWeek end. In other words, it would have been something maybe like 370 days, or whatever. Caveat Emptor.
Now - as for having your engine measured at a time other than a race event after setting a record: I know that the new Chief Inspector, Matt Schuss, would like to discover a way to have engines measured and sealed at places such as your engine builder's shop or your home shop or whatever. But that measurement would be performed ONLY be an SCTA-certified engine measurer - someone that is actively doing that for the Ass'n. That would relieve the impound folks of much hassle of the race event - by having that critical part of the certification process done in less hectic conditions. On the west coast - specifically SoCal - it isn't a huge job to find someone that could meet the SCTA's criteria as a reliable person to measure and seal. But - in much of the rest of the country there are no resident inspectors within reasonable distance of many racers.
A reliable person, to assume I know what Matt has in mind, in not just someone with the technical skills necessary to perform and record the measurement, but also someone with impeccable credentials - someone that would have absolutely no reason to cheat - using the crude term. For instance -- having your engine builder measure and certify his own work would be a no-way-in-hell no-brainer. Having someone that is actively racing a vehicle in any way similar to yours -- likely won't work. You can go on, but it becomes difficult to find a person to do the measuring - and then, compounding the felony, there has to be a method for that measurement person to be compensated for his time and travel to your engine's location at the time of final assembly.
We'd all like to have the measurements done in a convenient location but with absolute "security". If you know how to meet those two very different needs -- contact Matt. His number and email are in the Rule Book, and I'm sure he's interested in working with the racers. He told me so.