I personally don't want my software making any connections unprompted except if that is its primary purpose.

Updates for OSS is also often installed via a package manager so additional checks are less useful and generally unwanted. That leaves non-package distribution (e.g. Windows or portable binaries) - I think best would be to either ask during installation or ask once if the local clock is quite a bit past the release date of the current version.

Of course different people will have different opions on this.