Spark's intake recommendations are based on activity averaged over the entire week. The body has reserves of around 2000 calories of usable energy, and between the recommended intake and this reserve, will cope with most normal variations of exercise.
However, if you start burning 1500 or so calories in a day, you can get close to depleting this reserve of usable energy, especially if your recommended intake is based on a low
As a regular hiker and backpacker, I can burn over 3000 exercise calories per day on rough terrain or with significant elevation gain, and I'll often eat an extra 1000 calories over the recommended amount to compensate. And if I am pulling big miles 2 or more days in a row, I'll eat even more than that.
However, one word of caution. Calorie estimates for that level of activity can be misleading for a number of reasons (eg. calculators assume constant activity, but if you are burning that many calories, almost certainly there are some breaks in there). You may want to come up with estimates via several different methods to get a better feel for your likely burn.