I have narrowed my flooring choicesfor my bedrooms to an engineered flooring in either red oak natuaral or natural hickory(wife's preference). According to the vendor web site Hardwood Floors made from UV light sensitive wood will darken over time and that a small amount of change can occur in Hickory and Maple.

I have red Oak natural florring on the ground floor of my home, so I know what to expect if I go with red oak in the bedrooms. Does anyone have any input they can provide on hickory naturall? How much darkening if any can I expect to see if I decide to go with natuarl hickory?

Thanks

I wouldn't expect to see much more than you have seen in the oak.

Well actually you are dealing with two separate phenomena. While the finish will amber and reach a deeper mellow tone with time, regardless of type of wood it is applied to, various woods react differently to exposure to UV.
Some woods, such as cherry, walnut, and many exotic species do deepen to a richer but darker tone with time, others will have a lot of colour leeched out of them. One of these is red oak.
So if you are seeing a darker or richer tone to your existing oak floors, it is a change in the finish applied rather than the wood darkening.