I've seen some good reviews on Linux Lite so I decided to give it a try. It's a very polished light distro based on Ubuntu 16.04 LTS & XFCE.
The SanDisk Ultra 16 gb USB 3.0 sells for around $30.00 so not top of the range but good quality. I decided to try Linux Lite as a full install. After the full installation which went very smoothly I had about 5.6 gb of free space on the flash drive. It boots up to the log in screen in around 15 seconds and shuts down very quickly - in under 5 seconds. After using it for about 30 minutes the flash drive feels slightly warm but not hot. Internet browsing & other tasks seem to be perfectly fine.
I've tried full installs on flash drives before but this is the best by far. My main reason for trying this on the SanDisk was because in the last few months I have wasted far too much time distro hopping installing onto my main hard drive. (The distro I keep coming back to is Xubuntu.)