This can be a complex issue...but should only be so if you're planning to "critically" evaluate a beer; when drinking for enjoyment just do whatever it takes to get it to serving temperature. (salt water ice bath, 30 minutes in freezer, pre-chilled mug, etc.)
I've noticed a catch-22 with beers and serving temperature: too warm and the CO2 has not fully become solute in the beer; too cold and the CO2 refuses to "escape" from the beer. Either makes the beer seem flat...with the former causing a huge foamy head that falls fast and the latter causing no head to form.
There's laws that relate to how temperature, pressure, and volume interact to determine gas solubility in liquids...and I think they are laws which cannot be broken!
The homebrew club I'm a member of -- the Savannah Brewers League -- is one week away from our annual Bay Street Bash homebrew competition, and the topic of how to chill all the entries at the correct serving temperature, be it ale or lager, for at least 48 hours prior to judging, has been debated since last year's comp. (24 hours is likely enough, 48 is just for "sureness")
We all came to the conclusion that time and temperature do matter when it comes to producing the correct expression of carbonation in a beer...and that it is very important when a group aims to hold a quality-driven homebrew competition. Most likely we are renting two chest freezers and hooking them up to temp controllers; one for ales (~48 F) and one for lagers (~40 F).
In the future, we may buy two with club funds, and use them for group lager brewing when not in use for the comp.
euge, I had a bottle of Chimay red while brewing a Belgian Pale Ale last weekend...I'll bet regardless of how long you chilled it it was awesome