Over on his Japanese blog Nobu has uploaded a post showing how he modified his RTL-SDR dongle to be air cooled via two small PC fans (post is in Japanese but can be read with Google Translate – right click -> translate to English in Chrome).
By cooling the dongle, and especially the R820T chip, Nobu writes that he sees improved ADS-B decoding performance as his range is increased. Without cooling the R820T chip can get quite hot and causes failing reception at around 1.5 GHz. Passive cooling is usually enough to fix reception at those higher frequencies, but active cooling via a fan can take it further and actually improve sensitivity slightly.
To add to his post, we suspect that the sensitivity of the R820T/2 front end reduces by about 0.5 dB at most when it heats up (after a few seconds), so forced air cooling should be able to improve sensitivity by about this much.