synLogin() reference sufficiently explains ways to cache credentials.
The Connecting to Synapse documentation on the homepage could be updated to include the rememberMe=True parameter, which I think is a more accessible way for users to cache their credentials. Synapse docs will reference this code chunk.
, I created SYNR-1382 to track your suggestion. I will work on it on the next release. And change the title of this issue and close it as we verified that the vignette exist.