On the other hand, when we've had company parties at the office, I've seen people go back to programming after a couple of beers because they just had something on their mind that they need to finish.
People can certainly review something within an hour or so, but only sometimes. If you just had another interruption your juggling balls are still on the table and you haven't picked them up yet. So this is when you can finish a code review ten minutes after someone requested it. But if the request came in a couple of hours later, you wouldn't be able to take a look at it until the next day.
Culture can affect whether programmers are able to get long stretches at all. If they aren't, then they're obviously more available to short-term tasks such as code reviews. On the other hand, I know people who work best when left alone for days. There's no asking for a code review if the guy has been juggling since Wednesday because if you do he'll have to spend the next week as well working on the same task.