la sagesse de mon âge n'est rien au regard de l'étincelle de ta jeunesse, ne se compare pas, ne fait pas le poids.

ne pardonne pas mes années (en trop).

C'est le sens.

I read it rather differently than the others, I think. And first fo all, can we confirm the position of that semi-colon at the end of the first line? On the face of it, it seems rather an odd place for it.

I think the general sense here is:

"How could I have been so silly as to presume to have anything to offer you (in all your full bloom of youth)?
And yet, time is not going to be forgiving to your youth (and one day you're going to be old just like me)"

I rather see the 'yet' as being more like 'pourtant' here, though I'm not too sure of my ground in FR!