The longer the stay the better as we minimize costs. We also save time because more guests means you probably have to communicate more often.
Ideally you would want to gather your local data and see how many nights people book more often.
1-2 nights stay are terrible because they ruin your calendar availability. Lets say someone books 10 july 1 night. Another person wants to book for 1 week+ but your listing will not show up in his search for that date. You just lost a potential long reservation and inflated your costs.
1 night is good for last minute (last week) bookings as there could be lot of people who are passing by wanting to stay for a night.
There is also an idea of letting 1 night as long as there is another reservation on next/previous dates. You have 10-15july booked you could let 9 16 july for 1 night. The downside is we block a potential long stay that would book that day. It is a new strategy I am thinking so it could be wrong.
For a new listing I would set min stay 1 night in the first month maybe even 2 weeks only with a very competitive price just to get some momentum.