Vermiculite Topping - Yea or Nay

[FourOaks]

As of late I have been growing my seed starting operation, and need some input.

Im wanting to do away with using Humidity Domes. In short, they cost money. As it is, I have run out of domes, need to sow a bunch more flats, and dont want to buy more.

So, does vermiculite just help hold in moisture to the mix? Can you get by with just topping with V. and not worry about a Dome or Clear Wrap?

I have seen large commercial operations that obviously dont use any sort of covering. But, they have the Humidity thru the roof, and they often use a very quick draining medium that is watered daily.

So what are my options?