A brief expose should be fine since the machine is up to date. As Shonky indicated, make sure SSH is configured well. Ensure /etc/sshd_config has root logins off (most distros do this, can't speak for Mint). You can go further and require keys only. Or change the port from the default 22 to something else for a little security via obscurity.

My VPS sees a number of SSH attempts daily. It's set up to block the IP with the firewall if a few bad attempts are seen. Outside that, most attempts to get in are via Apache and various known insecure PHP scripts.