Elle if they were done correctly, they'll still be right! Our season is the same from cradle to grave. If you can't remember how to use your colours though, it might be worth thinking of a re-rate or something to get to grips with them again.
Faerie It's basically discovering your very best colours, the ones that make you look even skin toned, healthy, vibrant, stylish, younger, fresher, brighter, more co-ordinated, everything really. Wearing a palette that suits you, and dressing in clothes and make up that all co-ordinate, means that you instantly look more put together, it is far easier to have a capsule wardrobe as everything matches, and you generally look and feel more confident.
I don't know about other systems, but at House of Colour we first assess whether you have warm or cool skin tone by comparing various sets of drapes, and then we assess whether you need brighter or richer/more muted colours to look your best. We then sit you down and talk through what that actually means for you, how to use the information you've been given, ideas for putting colours together, how to shop with your swatch book etc etc. It's quite an involved process, and the classes I hold last from 9:30am until about 2:30pm, depending on size (I do 2-4 people per class). It's quite a chunk of money, so I am always determined that clients leave with something that is actually useful to them for the rest of their lives, not just have a nice couple of hours out and then forget about it!