You have some old windows. They are really old windows; Drafty, ugly awful old windows. Kids would throw rocks at them if they could stand to even look in their general direction. Now, they may not be that bad but to you they are. It is time to change them.
You have the money saved up. Saved up a lot in fact because you know the cost of replacing windows is extremely high due to estimates, contractors and labor. You know that even though your kids will not go to college now, they will have a great view from your new windows.