I try to keep my seasonal prices/minimum stay listed for about a year out, with any price increase generally after the first of the year. For example, for 2018 we've decided not to raise the prices, but to give a less generous discount for weekly bookings. It's already posted on all of our booking platforms.
That said, I was once caught off guard by someone booking almost a year out, before I had adjusted prices. I did honor the quote she received, but let her know that I was honoring this year's rate, and it would be higher the next year if she decided to book an additional visit (we attract repeat guests visiting family with small houses in our neighborhood).
Also, on another website, I had a guest who had not noticed the "from" in tiny print by the price, and was shocked at the difference between our Winter Bargain rate and the Summer rate. I frankly was uncomfortable about the way the pricing was laid out, so I honored the lower (Winter Bargain!) rate. It was only a couple of nights, and she was very pleased. I feel if I make a mistake, or the booking platform, as my agent, then I should handle it as I would like a host to handle it for me if I were the traveler.