I have 25 and it's my all-time high, but I smoke about 20 of them regularly. I smoke only once a day and not every day. What stops me from buying more (beyond the economic factor) is not so much having the embarrassment of choice on which pipe to use (if only!), but that it becomes difficult - with my rhythms - to smoke them all with the necessary frequency.Admittedly, the more pipes I acquire the harder it is to decide which one to smoke!
In fact, I am of the opinion that a pipe that has been sitting for months does not perform as well as one smoked regularly.