Not exactly how long my sign off inspection was, but it was no longer than 45 minutes. I think the big key to the sign off is when it comes to the A/C portion FWF. The inspector can tell right away if you have you ducks in a row by the way it has been put together. For example...the carb has washers on the outside of the rod ends to keep the rod end from falling off should the bearing fail. Fire sleeving of the fuel and oil lines (secured with SS zip ties) and the use of RTV on the ends of the fire sleeve. Proper firewall thru fittings for the engine controls etc. Use of adel clamps to secure lines and wiring. I had all the panels open for inspection (under wing, tail, hinged cowl cheeks). Be sure the A/C is clean ! Both inside and out. Leave NO FOD in the A/C ! By that I mean shavings, cut wire, washers, etc. Be prepared to start the engine. Good thing I checked the battery before he came as it was low and I charged it and ran the engine before his arrival.
I also had my avionics manual, engine log from Aero Sport Power AND my builder log from 27 years and he looked at none of it ? Not to say your DAR won't want to look at those Doc's, just be prepared ! If you OVER prepare you will probably not have any problems. Above all, as with any FAA inspection or test...do NOT volunteer any information.
Have ALL your required paperwork on hand. DOT the I's and CROSS the T's ! The EAA has an excellent package that will walk you thru the whole paperwork process. The entire kit is about $12.00 ?
RB