Booking ahead isn't anything to worry about. I'm set at six months in advance, but am very mindful of peak periods like the Formula 1 in Montreal, July 1st, Labour Day weekend, etc. I price my place very carefully on those days.
If you have your calendar set to 3 months (the minimum, I believe) you shouldn't worry about someone booking that far in advance. In fact, it will help you plan. I would also set your refund policy to strict. Not unless you are okay with people cancelling at the last minute.
I don't give discounts, although I do lower my price when I have mid-week days that are going unfilled. I drop the price the week before and usually do get a booking out of it.
I recently made the mistake of offering a woman a discount on a stay at a second Airbnb I manage for a family member. She was brusque and unappreciative and I could have easily booked someone else for more money. For some reason, discounts seem to either attract the wrong kind of people or make the right kind of people take you and your place for granted. It's human nature I suppose.