I've noticed this intermittently as well starting with 8.3, and am hoping it's fixed with 9.0. What version are you on?
It would be a shame if we had to upgrade to 9.0 to stabilize these connections.
maybe. You can check with Tableau support to confirm. I know what we had to do with 8.3 is manually update the data connection passwords (in bulk) on server prior to leaving work for the evening.