Some people dont believe in lowering temps. But in the BP's natural environment during the winter the temps drop to about 86ish during the day and mid 70's at night... so if you do drop the temps it shouldnt stress your snakes out. There is a good guide to gradual temp changes at
http://8ballpythons.com/journal/breedingcalendar.htm
by gradually lowering temps it will be easier on the snakes and not just an all of a sudden 5 - 10 degree drop in temp
hope this helps