@Tea8
Like @Susan151 says.....it is possible to have different "minimum stay" requirements for different dates/seasons/months.
Calendar > Availability settings > Availability > Trip length (Edit) > Add another requirement > Edit a requirement > During (drop down) > Specific dates
Then chose start/end dates and the min stay you want to have for that duration. Don't forget to click SAVE. One thing to note is you cannot have overlapping dates for requirements. For instance, the dates you put in will have to be something like this.....
During June 30, 2018 – July 31, 2018, guests stay for minimum 14 nights.
During August 1, 2018 – August 8, 2018, guests stay for minimum 2 nights.
During August 9, 2018 – August 23, 2018, guests stay for minimum 5 nights.