DBS checks don’t have an expiry date.

The government advice says this:

There is no official expiry date for a criminal record check issued by DBS.

Any information revealed on a DBS certificate will be accurate at the time the certificate was issued. You should check the ‘date of issue’ on a certificate to decide whether to request a newer one. In certain employment sectors, a new criminal record check may be required periodically.

You may also be required by law to carry out a fresh check of the DBS children’s and/or adults’ barring lists in accordance with sector-specific guidance.