I agree with picking them when the tendril closest turns brown but so long as the vine is still alive you can leave them on. If the vine starts dying or rotting because of frost definitely pick them. Why do you want to hide cute little jack-be-littles under paper? A cool dry place like a basement is an excellent place to store them if you want to keep them as long as possible. Unless the pumpkin is damaged or not ripe I am sure you can pick them now with no fear of them rotting before October even if just sitting in a living room. Healthy pumpkins can keep for a long time I still have some pumpkins from last fall completely fine with no signs of rot and they are just in my living room where I can admire them.

If you want them to keep as long as possible what I do is just wash them well with ordinary soap and water or some people recommend washing them with one part bleach to nine parts water. Then I store them uncovered in a cool, dry place like a basement. Repeat the washing as they begin to get dusty from sitting around, maybe like once a month to every other month.

How nice. I didn't know how long they lasted.

Oh, I get it! The ones I buy in October every year were probably picked in Early September!

Well, I said I didn't know what I was doing :-)