That's a very weird sentence, iamtime. None of your alternatives is correct.I have to live longer than I have planned and to grow younger than I have lived, so that you still can remember my youthful face when we meet once more in a decade and decades.
Whilst not understanding the first part of your sentence, you could end it like this:
'. . .when we meet once more in a decade' or
'. . .when we meet once more in two or three decades.'
Even those constructions don't sound natural. I'd say '. . .when we meet again in ten years' or '. . .in 20 or 30 years'.