Yeah those five extra minutes are clutch fr. But honestly if your skin is really dehydrated, that mask was probably doing most of its work in the first ten. The real game changer is using a thicker moisturizer right after you rinse it off to lock all that water in. Otherwise you're just letting it evaporate back out. Gotta seal the deal.
Actually I think that extra soak time makes a real difference. My skin feels way more plump after a full fifteen minutes versus just ten. The mask has more time to really sink in deep before you even start with moisturizer.