Maybe 6 months is too much, but for example in Europe, you do need more than a month to ensure that your grid actually works even if you have low wind and low sun for that long - at least until you can over-generate so much that you have enough production on a ~14h of sunlight on a cloudy day in winter with low wind you can ensure enough power for the whole day. The farther north you go, the bigger this problem gets - places like Norway or Finland have far less than 14h of sunlight in winter per day, for example, for months.

Why the heck would you rely on solar power in Northern Europe? The North Sea has some of the most reliable winds in the world, and Northern Europe is full of mountains. Use excess winds to pump water up the mountain and use the head to turn a generator on the rare windless days.