I usually set the span to max. This minimizes short-cycling, allows the HVAC to run more efficiently, and more effectively moves air around the spaces.
14 Forester XT Touring FA20DIT (Cobb Stage 1)
Castrol Magnatec 5W-30 D1G2 + FU filter (72,320mi, 8/24/19)
15 Legacy Premium FB25
Magnatec 5W-20 + FU filter (47,300mi, 5/11/19)