You can 'renew' it early, for another 10 year validity, but no guarantee that it will be at the same rating on the new one.

I bought a house in January rated D with 2 months left so I had it assessed early as I was going to rent it out and it was rated C. I hadn't improved it and there had been no major improvements in between assessments.

I’m not sure if you are aware but they have just massively changed the epc input requirements last week which will now take into account the individual size of each window and the properties orientation, these changes came in last week I believe so this will definitely have an effect on any future EPC’s

If I had to guess now, it’ll be a D with the way it works.