Generally a Module B certificate should not expire as its related to the technical design of a product. However in case of DWD regulators have imposed a regulatory expiry date to the certificates. This deadline is 5 years.
It is unclear what changes will be processed after this 5 year period and if new migration testing is needed. But a review against the EUPL (ie to check again on expiring materials) will be needed.
Module D certificates are also valid for 5 years.
It is also unclear how approvals for site-applied materials will be handled as these are once-off approvals of technical designs. This will be clarified under the NB-DWD in future.