Both PE and Ian Grant commented in the past that it's good practice to let D76/ID-11 sit for a day before use. IIRC Ian said it's good practice to let it sit at least until the next morning.
I've found on the 22nd December, 2009 PE wrote the following on APUG in the thread "D-76, pH elevation with storage":
When I have mixed D76, I bottle it in air tight containers and use when it has cooled, which may be several days or weeks later. Are you suggesting that when I mix it in a bucket I should leave this for 24 hours before storage to allow contact with air for this oxygen thingy?