@Lucy168
What you are trying to do is technically NOT a long-term stay - it is just repeat business IF the guest really does continue to stay every Mon~Thur for the next 2 months. If it were me, I would be very very cautious about sending any type of special offer or providing a discount for such a set-up. It's not a weekly or monthly booking so such discounts shouldn't be applied. Rather, you could consider a discount or special price for REPEAT business.
For non-consecutive stays, technically the guest must check in on Monday and check out on Thursday - meaning your listing SHOULD be available for other guests between Thursday~Monday. Even if you don't want same day turnovers you would be able to host other guests during the weekend (Friday~Sunday).
IMO, if the guest wants to "leave a couple things" with you during the weekend, they should absolutely just book for the full 2 months. Also you should not be blocking dates without a reservation, the guest needs to make a firm reservation for the dates they want.
I've hosted a lot of exchange students for up to 4 months and during their reservation, they take extended weekend trips or even week-long trips with school friends. I've NEVER had anyone ask for an additional discount because they will be gone a whole week out of a month.