Validity of pedhinama in gujrat

In Gujarat, a Legal Heir Certificate (Pedhinama or Varsai certificate) is generally valid for a lifetime and does not require renewal. Once issued, it remains valid indefinitely, with no expiration date. 

The registrar cannot demand any such new certificate without any law governing this requirement, you can ask him that under which authority he requires new varsai certificate and file a writ petition against him before high court seeking dierection against him if he is not cooperating

Once the  certificate has been issued it is final for life or till there is some change in pedigree  (by death of LR)

Yes, the officila is overeaching. You may seek appropriate information under RTI Act. This could wake up him correct his mistake/mischief.