A question about white wine.

[sensesworkingovertime]

Does anyone know how long a bottle of white wine lasts unopened?
I think I've had it about four years and it has been stored in a mostly very cool dark kitchen cupboard (standing). It is Welsh, not dirt cheap but not very expensive. Thanks in advance for any advice MNers.

It would have been better if it had been lying rather than standing. It probably is still fine but I would recommend your opening it at home for yourself rather than serving it at a dinner party, as it may have gone off.

Welsh wine?