Certified GKH Gardening Expert
It is just aging. The vine will become less vigorous as it gets older. The cold won't really bother them much.
It may be time to dig up old vines and replant if possible. Otherwise, restorative pruning, which can be quite drastic, will help them to get the most out of them. This article will give you more information on the plant: https://www.gardeningknowhow.com/ornamental/vines/virginia-creeper/virginia-creeper-maintenance.htm