For regular updates and if you're used to it, it doesn't take more time then 1-2 minutes.It's like: Stop server, download and extract new version, run upgrade script, start server
That's all fine and dandy on a locally-hosted OC installation, but completely impossible on a shared hosting people may use for availability reason.
The first or second command line for an upgrade, according to OC's manual, is:
sudo -u www-data php occ maintenance:mode --on
There's no such thing as sudo on a shared hosting, or the provider has more serious problems than supporting an outdated version of OC.