I spend a few nights a week testing out overnight masks. It doesn’t take me the whole night to test them, obviously, I just slap them on (takes approximately twenty seconds) and then go to sleep. It’s one of the easiest jobs in the world, unless there’s a job that just involves going to sleep and not even applying a face mask…
Anyway, I record my results in the morning and jot everything down in my little notebook of face things and then, if I’m not impressed, I move on to the next mask. If I am impressed then I’ll put the mask to one side and test it out a load more times before it joins a little shortlist and then I do a sort of “X Factor Six Chair Challenge” thing, except that there are only five chairs, because, for some reason, it’s always “top five”, isn’t it" Or top ten" So here are my top five overnight masks. The ones that I find really hydrate and plumpify and leave the skin looking juicy and gorgeous in the morning. Truthfully, I don’t think that there’s much difference between a lot of these overnight masks and a rich night moisturiser, or rich any moisturiser, but two thoughts:

you probably apply a little more of a mask than a night cream, merely because that’s what you do with masks, and so perhaps it’s slower to absorb and the hydrating powers are a little more long-lasting
many of them are much cheaper, per ml, than night creams and appear to ...