I have been in lots of pubs and when i am on a pub crawl i always start at opening time and often wait for a pub to open and when i have entered the pub the landlord/lady will either pull a couple of pints off or say i have already pulled a couple of pints off.
Beer should be served at the correct temperature whatever time of day is,if you went in a restaurant and a meal was served cold but cooked properley ime sure you would take it back.