So you're trying to limit your purchases to once a month?
And how much do you buy? And 8th? A quarter? I understand your concern re: not smoking excessively but I wouldn't worry too much about how often you're copping- given that it's not legal in your home state yet, it makes sense to buy in bulk and always have a little extra around just in case. The important thing is that you gotta decide on an acceptable daily/weekly/monthly intake and do whatever you can to stick with it.
Of course, if you're trying to take breaks between purchases to re-raise your tolerance, that maybe gets a little trickier, since it's hard to resist smoking if you've got weed. But maybe something to work towards? Either way, I vote that you cop before the festival.