Wellll would it make more sense for you to boil the first 5 gallons while mashing the 2nd 5 gallons? Like just doing 2 x 5 gallon batches instead of 1 x 10 gallon batch?
I haven't let wort sit for too long, but, I'd think you'd be ok letting it sit for an hour + as it WILL be boiled anyway. Could be an opportunity to check out first wort hopping too!
Remember, 'cold' is a flavor
Cooking with beer? Been doing it for years.
Add it to the food? I'll have to try it sometime.
He who has tasted sailing will walk the earth with his head turned into the wind.