The advantage of a 30-day rental verses something longer is that it is at that point it is considered a long-term instead of a short-term rental. Lodging taxes have to be collected on short-term rentals owned or managed by a business. However, lodging taxes are exempt from long-term leases. The savings in taxes can often cover the costs of several days lodging, making it more cost effective for the renter.
The reason I know this is because I used to run a B&B with my husband, at which we had to collect lodging taxes on any reservations lasting less than 30 days.