Tenant wants to terminate lease early, should I make them pay the entire penalty?

[Craig McCarter]

I have a tenant that has been in my home for almost 6 months. By all accounts they have been great tenants. They keep the home clean, pay rent a week early, and I haven't been called out to fix a single issue. They are a young engaged couple, and we actually have a few acquaintances in common (a connection we discovered when they were moving in).  He just informed me he got a job in another city and may need to break the lease early. The lease says in this situation the tenant owes the total balance of the remaining term. But that feels a little harsh. I am pretty confident I can fill the vacancy immediately, and probably charge a higher rent as well. This would be close to a $15K penalty. I try to stay on good terms with people as word of mouth can always come back to bite/help you, and generally try to treat people with what feels right/fair.

I was thinking I charge a one-month penalty for breaking the lease, and they continue to pay rent until the unit is filled. Basically I get one month of additional rent for my troubles, and the rent is paid in full throughout (either by them or the new tenant)

Am I letting them off too easy? anything I may not be considering?