Is KfW 70 worth it in 50 years?

Since the house in its final form (dimensions, sqm, etc.) was not definitively fixed until last weekend, but changes were still being made, a corresponding calculation could not yet be carried out. From my point of view understandable – you have to know whether to calculate the heating requirement for 190 or (now probably finally) 170 sqm. The planned house is now going back to the structural engineer ("final check"). After that, the calculation of the heating/energy demand will take place. Then it should also be clear which measures will actually be taken or not and what impact this has.