There was a slight stretch out, but it wasn't to a point where it was no longer stretchy. For residue and buildup from hair oil and product, I simple toss the twistbands into a delicates laundry pouch and wash them in the washing machine.
I wear mine on my wrist every day. I also shower with it on my wrist. I used the same twistband for over 4 months before I noticed any change in the structure. When using a standard hair tie in the same manner, I noticed that it stretched out and some elastic broke within the first week.
Heat seal the ends as soon as you get a Twistband so it doesn't fray. When it stretches, wash it in hot water in the sink and hit it with a blowdryer on the hottest setting. Or throw it in the dryer with the damp clothes.