Redoing medicals without Immigration mission's advice is not recommended, from my opinion.
Because, decision is not made yet on the case. If interview is required, then redoing medical from applicant's part is not of good use. It's difficult to figure out how long it will take to schedule for your interview.
Some missions, like Singapore, Islamabad, Srilanka and other Offices who takes longer processing time, normally schedule interview in 12 to 24 months. Therefore, redoing medical for these mission are not useful. Should wait for their instruction.
Sometimes, decision is not made even in 12 months based on individual's case. So, medicals got expired. If VO decides for interview, they will not ask for another medical before interview. Positively, asking for redoing medicals without interview is a good sign.
So, my suggestion to all is to wait for their instruction. I am agree with few members here that medical form and procedure is as same as it was done first time. I am also agree that Updated / validated medical result could make Visa office process application faster. But it will help those who are confirmed by Visa mission that their case is finalized okay. Otherwise, how could u be so sure that you would not be called for interview?
Except sending updated supporting documents, applicant should not do anything in advance without mission's advice. Mission officers may not like it that way. They might treat your case with extra interest, means it will take more time.
Just relax. Instead of controlling from applicant's side, let it be on Mission's control. Let them work their way.
Cheers