Direct sunlight duration plays a large role in how well your deck ages. If you get direct sunlight 5-7 hours a day, the sun can evaporate any accumulating moisture. Moisture is the # 1 cause of rot and with out the sun it will take a toll much faster.
If you do not get enough direct sunlight it is important to make sure that any moss or mold growth is removed and treated in a timely manner. Moss and mold thrive in shade and damp areas and will promote rot in your decking if it is not addressed.
The elements can play a large role in how much your wood deck weathers as well. It is highly recommended that all wood decks be painted, stained or given a clear sealant to protect your wood deck from moisture, sunlight, wind and dirt. I Build myself a red cedar deck and after a year that rich color faded to a grey color. I stained my deck and a year later the stain started to chip and fade. The following year I re-stained and put a clear sealant over the coat of stain and the stain lasted 2 years. From my own experience I would highly recommend using the clear sealant which creates a barrier that will protect the wood for up to a year. Benjamin Moore carries a few different brands and I found that they all work the same. Speak to an employee and they may recommend one more suitable for the amount of sunlight and moisture that your deck is exposed to. Again these recommendations are for decks in Suffolk county NY.