piecemeal purchase of additional scores

Hi!  I am not a professional musician, but I use noteflight occasionally to arrange fun tunes for particular ensembles (eg. for my 3 young children to play together on their violins, at their level) -- sometimes I go years without making anything new, and sometimes I create 4 new scores in a matter of days.  I do not have a real need for your full premium subscription, it would feel like a real waste when I don't touch the website for a year or more at at time.  But I would eventually like to be able to create and save more than just 10 scores.  It would be incredible if you could add in a pay-as-you-go plan of sorts, ideally on a per-score basis!