I would probably say more so a reason to get it serviced. Boilers of any sort should be run for at least 30 minutes per week to ensure maintenance.
As a landlord, surely you have a legal requirement to be ensurring that all appliances are safe and in working order? I always used to ensure I saw a gas safety certificate and servicing certificate for boilers. If tenants don't use the heating, that's their perogavtive. If you don't want it in the apartment have it permanently disconnected.