I hired an electrician to do EICRs for the tenanted flats at my old
office. He has produced certificates with a one year renewal, rather
than the usual five years.

There's nothing 'electrical' to justify this. He just says that the
tenant may leave, and then he thinks I should get a new certificate "in
case the tenant has modified the electrics".

Is he right, or has he invented a little dodge in the hope of having
ongoing work? If so, apart from refusing to pay his bill, is there any
way to get him to reissue the EICRs with a five year renewal?