Another thing... thermoregulation becomes important when a snake is dealing with extremes - ie, 110 degrees under the direct sunlight. At this point, of course they will seek shade. A constant temp ranging from 75-77 at night to 80-84 during the day is HARDLY an extreme by which a snake would be uncomfortable enough to need to cool off.
No Ken. Snakes thermoregulate to acheive certain life events. Yes they have behavioural mechanisms to AVOID temperature extremes, but when the air is a balmy 84F, boas will STILL choose other temps at certain times to acheive certain tasks. THAT is thermoregulation. Cooler temps to produce and move follicles around, higher temps to gestate or to digest food. Cooler temps to conserve fat reserves or energy (its WHY reptiles are 10000x more efficient than mammals). Etc etc etc.......