The BJCP class I took recommended swirling the beer when judging and evaluating a beer. We were also recommended to really try and get a good sniff in when the beer is first opened and poured as a lot of the aromas, especially hop aromas are extremely volatile and are only present for a short period. Swirling the beer causes some co2 to come out of solution and carry with it aroma compounds, so this might be beneficial. Another technique that is taught is to exhale through your nose as you swallow the beer, this takes a little practice to get the timing right, but you can pick up aromas you don't otherwise get by doing this. Again, this is all techniques taught in a class I took.
All that being said, I'm not sitting down at every bar I go to and filling out a score sheet and spending 3-5 minutes evaluating 3oz of beer. In fact 90% of the time I don't do any of this. I order a pint, I take a quick sniff and enjoy. If I am sitting around with some beer buddies and we are pouring sours or high end, complex beers into snifters or tulip glasses I am taking the time to evaluate and enjoy all the labors of the brewer. I tend to go through this process with my own home brews to pick out flaws and successes and take note. This does involve some swirling and I have never sat down and had a beer oxidize in front of my eyes, or overnight. You know that beer that doesn't quite get drunk before you fall asleep on the couch -- take a sip when you wake up. It might be flat and warm, but surely its not oxidized. Oxidation take some time.