How long is it reasonable to delay the delivery of the epidemic?

Affected by the epidemic, developers can't deliver the house on time, and the delivery time can be "reasonably postponed". The specific extension time can be negotiated with the owner. However, there is one thing that needs special attention. This time cannot be extended indefinitely, as long as the epidemic has not passed, it cannot be used all the time. Developers can talk about the epidemic situation because the epidemic situation is legally force majeure, and the application of force majeure is closely related to the actual situation.