Renters breaking lease

[Bradley Snyder]

I have a home in Mt Laurel NJ that I am renting out. My tenant asked to break their lease 4 months early due to them buying a new home. I told them I would do it if they pay at least 2 of the remaining months to cover me incase the house needs repair and sits for a while. The tenant sent me a law in NJ that states the tenant can break their lease and would only be liable for the days it sits empty and said they would do that instead. My question is, if the tenant just bails, am I only able to hold them liable for the period it’s empty or the term of the lease? If this is the case, why even have a lease expiration date if the tenants can leave whenever they want?