You must make multiple backups from your seed + print it out and store it in a secure place. SEED is the most important part of your Waves Wallet besides the Waves+Assets you are holding in it, of course.

I tried both the Github download and the Chrome addon version of the Waves Lite Client wallet for the mainnet. Both forget all of my prior login info every time, with me having to not just re-enter but re-create anew my login and password starting from the multi-word seed.
Essentially, it ends up back at the "register" phase instead of simply a "login" phase.
Now I will have to waste time doing a small test deposit and withdrawal, to see whether or not the wallet forgets / deletes my prior currency balance as well or not.
It is possible that the wallet was developed by people who do not realize how not everyone wants to have browser settings rigged to permanently save cookies or local login data. One could almost excuse that for the browser addon but not for the version which has subdirectories on my hard drive.
But, until Waves can recognize and fix a glaring issue like this, it won't go anywhere.