It'll only be 2 and a half hours out of your life.....and just out of spite!!! I always pour the last glass down the drain.
Keeping it cold is definitely better...plus it stimulates the digestive tract to "go"...so a double good.
Keeping it out for the 10 or so minutes between just takes the chill out of the stuff....
I've done 7 c-scopes...6 with the gallon prep....I'd take it anyday over the Fleet crap.
What time is your c-scope tomorrow?
q