SHT is an appropriate name for those sensors...they are kind of SH(i)T. Though the SHT2x are a little bit better I guess.
They seem to work best if they aren't near their range limits (especially high humidity) and if you don't have them powered continuously. I wasn't trying to conserve power since I was making a wired unit but even so I had best results powering up, waiting a short time for the SHT to stabilize then taking one reading and powering off until next poll (10 per hour)