What is reasonable access?

My landlord is selling the apartment, because of that we cannot renew the lease. It has been almost three months that we deal we awful brokers asking multiple times per week (up to 5 times) to access the apartment. Four different brokers came. When we said No (only once out of more than 30 visits), our landlord insisted that we gave access. The problem is that our lease ends soon, and that we need to stay an additional month at the end of the lease. Our landlord agreed to that (not in writing). If we limit access to our apt (once or twice a week, to a single broker), can he retaliate and ask us to leave at the end of the lease or does he need to give us a 30 day notice period even after the end of the lease?