I've only had my Tritronics collar for a few months, so I know nothing about the SD brand.
But, I've hunted about 7 times (4-5 hours at a time) this season and haven't recharged it since the initial charge when I first brought it home. The TT collar is supposed to have a rapid blink when charging is needed, if I remember correctly. I don't know if the SD brand is similar or not.
I don't know if the batteries used can develop memories, but I'd be leary of charging after every use.
From the sportdog website...
http://www.sportdog.com/basicfaq.shtml#4
How long do the batteries last?
Battery life varies greatly depending on the type of battery, how you use and maintain the product, as well as the operating temperatures. Please call Consumer Services at 800-826-5527 or consult our online troubleshooting guides if you have questions on your
specific system.
HTH,
Robert