I too read that the integrity of ear-impressions is lessened after 2-3 weeks.
However, when i got my ear impressions made yesterday, i was told by the audiologist that they are made out of a silicone compound, and will not shrink or decay. I'm gonna take his word for it, though it probably won't be a problem for me, since mine are already in express mail to JHA.
On that note: I Visited an Excellent Audiologist/Hearing aid Center in San Jose California today:
Contact Us
Great experience, really. (Thanks hifidk !!!).
The audiologist first checked my ears, using a really neat wireless ear-camera-probe-thingy and i got to see the inside of my ear on the monitor... Did you know your ear drum is translucent? I could see the little bones in my ear through it! Didn't know that was possible!
Anyway, he was quick and efficient about it. Stuck some cotton in my ear, then the RTV silicone in my ear. Got a real bite block which was slightly wedged shaped with 3 different ridges for biting (different measurements of bit. i went with the smallest). done in 15 minutes.
The best part? Total cost of Impressions/appointment? $20. For BOTH ears. yeah. pretty excellent. Including a bubble wrap pouch and shipping box.
perspective: next cheapest option within 15 miles: $25 per ear.