Remember that a larger story can often be broken down into smaller chapters or episodes. If you are releasing ongoing updates then this is certainly a viable method, as Nerds can attest with Some Bullshit.
I don’t mind long-form games, but I do find it a small pain if it’s not done episodically and the expectation is to play through the whole game each time for the new content if previous saves aren’t compatible. It would be much appreciated in those instances to provide a dummy test save along with the update release if possible so that players can get straight to poking at the new content.
Short games are fine for delivering on a fun, intense experience - a simple, solid idea that can stand on its own. Long-form is arguably better for building a deeper connection to characters or the setting, however there is always the fear that a hobbyist dev could be biting off more than they can chew.
Also worth noting that you can also flip the above situation around: rather than have a large game broken down into episodes, you can release small, individual games that, as a series, flesh out a larger setting overall. Think UrgUrgUrg’s Huge Hallows series and the exploits of Gong and Fizzy.
Ultimately it comes down to personal choice as a dev. What is the best game length? Whichever one you feel is most suitable for the game you want to present. If the game is good you will find an audience and fanbase, regardless of its length.