it's probably just a wording thing, but your beer shouldn't be fermenting in secondary. before transfering from primary, make sure fermentation is complete (stable gravity reading over 3 days).
if i understand correctly, you are looking on information/recommendation on dry-hopping 5 days vs. 10 days. 5 days should be plenty. i read somewhere (can't remember where) that hop aroma peaks 3 to 5 days into a dry-hop.