I know that L&L regularly has discounts on Scrivener in conjunction with NaNoWriMo. Are discounts on Scapple offered at any predictable intervals?
Although we don’t make a big deal of it, or provide a free version during the event, Scapple has always been included in the NANOWRIMO coupon code, and with the 50%-off coupon that winners get.
So there is your predictable interval. 