So, unless all lease singers file for bankruptcy, they can’t stay for three to five months without paying rent, right?

Since these stays are shorter than LTR, it makes sense that tenants expect a less burdensome application process.

We've been seeing a rise in iffy inquiries for mid-term stays lately.

You will be surprised how many fall out deals I see from new and experienced investors that try to shop it based on rate and fees. 

EDUCATE YOURSELF - yes, it will take time, but will lead to a selection that better meets your expectations & avoids potentially costly surprises!

Would you think changing my minimum stay on Airbnb would be worth it?

Overall, this seems like a strong deal, but make sure to factor in potential surprises or changes in market conditions.

Rent out the ADU as a STR (7 day stays or less).

That could be a short term rental where people stay a couple nights at a time, someone coming to town for a work purpose for a few or several months at a time like a traveling nurse who signs a contract for several months. 

I did delist the ad and relisted in approximately 4 hours , to my surprise, the days got reset .