Hi @Susan5170 !
Agree with @Mike-And-Jane0 , recent market research (economic factors) indicates guests are booking more last minute and for shorter stays this year.
Also, if you keep the 5night min stay, you appear less often in search results as compared to a 3night stay. Why not try it out? You can also keep your global calendar setting at 5nights, then use a 3night min stay Rule Set and apply to specific dates on the calendar.
Hope it picks up for you. Let us know how it goes!