I am currently training a few new grapevines to the vertical, final height will be approximately 5.5' high. Next year I will train 4 cordons per vine to the horizontal.

When the vines reach maximum required height of approx 5.5', should I prune through the top node to allow the remaining growing energy to go into the "trunk", or should I allow the vines to continue growing and prune to height in January when dormant?