Some of the best thermal imaging performance comes from using Cryogenic Cooling to chill the imaging sensor down to temperatures as low as almost -200 Celcius (77 Kelvin), to reduce thermal ‘noise’ from affecting the sensor's imaging performance.
In thermal cameras Cryo cooling is primarily done by sterling type coolers because of their low SWAP characteristics and high cooling efficiency at cryogenic temperatures.
The biggest Downside to Cooled thermal Cameras is Maintenance Interval/Expected Life of many cryogenic coolers. Since Cryogenic Coolers use moving parts to displace thermal energy, they will eventually succumb to wear at those points of contact. Depending on cooler design, gas seals can also deteriorate. This allows for the thermal transfer medium (usually compressed helium) to escape the displacement chamber. When either of these things happens, the cooler must be replaced or rebuilt and recharged which can lead to camera downtime and costly repairs.