The official line is 'no power for 5 minutes clears all adaptive memory.' However, I think that this is the case where the question went through 10 people and each person doubled the previous person's answer. The specs I've seen indicate that KAM should be clear in 2-6 seconds, depending on the PCM, but I've heard many people swear that it takes considerably longer than that.

1999 Contour SE Sport MTX75 T-Red/Grey
Audio: Pioneer DEH-7400MP (MP3 CD), Pioneer TS-A6857 front & rear, PPI PCX-250, Infinity Perfect 10.1
Other: cup holders, cargo net, Blizzaks, Potenza RE950s