massachussetts child support calculation

i have been separated for 5 years. no legal separation aggreement exists. child support has been paid based on the massachussetts child support guidlines. from the age of 12 - 18 the guidelines provide for an increase in the basic support order of 10 percent. my daughter will be 20 in june and is a full time student. i have been paying the extra 10 percent even though she is beyond the age of 18. after 18 the guidelines say the extra 10 percent is at the discretion of the court. i want to stop paying the extra 10 percent as i have also been paying 50 percent of her college expenses and will continue to pay this for the next 3 years. my question has to do with under what circumstances would the court order that the extra 10 percent continue after the age of 18. i want to make sure i am being reasonable in stopping the extra 10 percent. my daughter also works part time and takes home between 50 and 100 dollars per week on average. my wife works full time and makes 54,000 per year while i make 67,000 per year. does anyone have any experience to draw from in regards to this question?