[And no, "slow leak" doesn't refer to relieving oneself by the side of the road while the others wait, impatiently...    ]
 
While on the GDB ride on the 29th, I started to feel unusually harsh bumping coming from the rear wheel at one point.  I pulled over and looked at the tire, and sure enough, it was VERY low -- but NOT flat...  Instead of changing out the tube (in the cold, and in the ditch) I spent a few minutes pumping additional air into it, and got back on the bike, hoping it would last a while.  Well, it dropped down to its previous semi-flat level fairly quickly, but basically held SOME pressure for over 10 miles, getting me to the next rest stop.  I proceeded to change out the tube in the comfort of the gas station restaurant, and was fine the rest of the way.
 
Once I got home, I tested the tube under water, and found a tiny leak, indicating a slight puncture through the tire -- probably a piece of glass.  However, I was somewhat mystified by the tube's ability to hold pressure for those 10-12 miles!!!  I then remembered that, when I removed the tube from the tire, the tube had "glued" itself to the inner wall of the tire, and had been somewhat difficult to remove.
 
I'm assuming that this is what allowed the tube to hold pressure - that once the glass/thorn/whatever departed, the tire sealed back up (mostly), preventing the tube from leaking all the way.   Anyone else had a similar experience with a "slow leak" or "partial flat"????   Opinions???

I've had tire leaks that acted that way. I always figured the tube rubber had to be stretched enough for a really small hole to leak, and low enough air pressure effectively sealed it.

Nope, it was the rear, a Kenda Primo (I believe).  I have a Racer on the front, but both are 1" width.