@Elna20
For sure, this is tricky if your area mostly attracts tourists because very few tourists are going to book for 90 days!
I host long term guests (anywhere between one and six months) so 90 days would not be such a problem for me, but I'm in London so most of my guests are coming here for work or study. I have a monthly discount in place but I also keep the rates lower than I would if I was hosting tourists for short stays. Don't price too low though as you might find it's not worth it once your bills, mortgage, taxes and other expenses are paid.
You will need to try to attract a different type of guest. Airbnb has said that stays of one month or longer now make up 25% of their bookings and are on the increase (up around 33% from last year) so there is a market for longer stays. I just don't know if there is a market in your area.
You might consider doing some direct marketing yourself. Are you near a hospital that has visiting doctors and nurses? Are you near a university that has travelling academics or foreign students, or even students from the island coming for short courses? Are there any multinational companies who might need longish stays for employees coming from abroad?
When I first decided to focus on long term stays, I posted this thread and got some useful advice from other hosts: https://community.withairbnb.com/t5/Hosting/Attracting-Long-Term-Guests/m-p/697467#M164398
Perhaps there are some suggestions there that could help you.
