It really depends on in which REM did your WILD happen. At the beginning of your sleep, very first REM is only about 10 min long and the nREM is 80 min long to form a 90min sleep cycle. These cycles repeat during your sleep. Each subsequent REM is little longer and nREM shorter, untill nREM is about 10 min and REM about 80 min long. So longer you sleep, longer your REMs are. But of course, that that's just a potential for the length of your dream. Happy dreams