Then it sounds like better preservation would be expected. The article says it lasts two weeks at 10°C. I have no idea how exceptional that is as I've never knowingly stored lettuce at 10°C, but it probably doesn't last as long as lettuce as refrigerator temperatures.
Http://cooking.stackexchange.com/questions/33540/does-a-head-of-lettuce-really-need-to-be-refrigerated gives a table showing that leaf lettuce at 10 degrees C evaporates only about 30% faster than leaf lettuce at 5 degrees C. That difference isn't that large.
It also gives head lettuce at best two weeks at five degrees centigrade. So, two weeks at 10 degrees seems a good result.
On the other hand, the article says _about_ two weeks; they might mean 'ten days plus', and 'freshness' may be highly subjective (I bet there is a standard for measuring lettuce freshness)
Humidity is a huge component of lettuce lifespan. You can't just plop lettuce into your fridge near 0c as it is quite dry (hence why fridges have crispers that maintain higher humidity for veggies, and are selectable to low humidity for fruits).
Frankly, if you're not using a head of lettuce in 2 weeks something is wrong with your eating and/or buying decision making :-)