Admin mode won't help. It really is just a way to enter your password once, and then not have to enter it for five minutes, even if you do things that would ordinarily require entry of your password.
Tunnelblick does not normally need to secure configuration files after an update. However a year or two ago the security settings of new configuration files was changed, and a recent update (a couple months ago?) required the stronger security on old files. That was a one-time issue, although I can't guarantee that something similar won't happen in the future, it seems unlikely.