E6 is like 3-4 bucks at Walmart. That 2oz tube lasted my whole build. I have a snap on the tops of the thighs and 2in wide black elastic (also at wm, 3 feet for $1.44 in the sewing section) that connects to snaps I've put in a regular belt I wear under the armor to hold the thighs up. I've trooped 3 times and already know my thighs will have to be changed out after I get to about 15. A boba fett in my garrison finished his build earlier this year and already had some areas dry rot, so the stretching isn't the only factor that effects elastic.
I suggest always use snaps where you'll have elastic, unless your using those screen accurate metal loop things on the torso that TM does. I don't understand those, I just did my armor to be durable, dependable, and long lasting.