The aging of a hardwood floor is certainly not something to get hung up about as this is all part of the natural process. If you are concerned that your floor is changing, rest assured that although it is true that there will be a noticeable difference in shading over time, this can be viewed as a good thing.
As the floor gets older and the wood and finish go through oxidation, due to the ultra-violet light from the sun, the colour of the wood mellows and deepens.
If you have a lighter shade of wood flooring, then this colour change will be more predominant as it starts to darken. There are also certain species such as Brazilian cherry and Iroko which are known to become darker naturally.
This whole process does take time so you might not notice any difference straight away, but it will happen eventually, even when the sun exposure is indirect.
The colour change is just part of the natural characteristics of using wood as a flooring solution and it can really make the floor look warm and inviting. So as long as you are aware of this from the outset, and continue to keep it well-maintained, you can always get enjoyment from your beautiful wooden floor.