Stockpiling Saturday: Diaper Stockpile – When do I stop?

I’m a sucker for cheap diapers.   I don’t know what I’ll do when my son is out of diapers!  What will I get for cheap then???  Which brings me to my question – With 650 diapers stockpiled, when do I stop??  Our little “Bug” is 18 months old.  I see us starting to potty train after Christmas.  I don’t really plan on using Pull-ups.  I don’t particularly like them.  But this isn’t a parenting blog, so I will leave my opinions on that to myself.   
Back to the stockpile.  I have no idea how many diapers I use in a week or month.  I always have two packs open at a time because I use Pampers at night and other brands during the day.  We also have to send diapers to daycare so it’s not like I can say, I opened this pack on Monday and this many diapers lasted until Thursday.  Doesn’t work like that for us.  So I haven’t tried keeping up.  My best estimate is 7-9 diapers a day.  By that estimate, we have 90+ days worth of diapers just in our basement.  Not to count the 5-7 days worth in the diaper cabinet and at daycare.
So I know we have enough to get us until mid-August even if I don’t buy anymore.  So, and this may be a rhetorical question, but do I buy if I see a good deal or do I wait a few months before buying more?  Feel free to chime in on the comments section.  :)
Do you have a stockpiling weakness or pictures of a really awesome stockpile?  Blog about it and leave it in the linky below!