Reliably run one-shots?

Mine usually do too. I tend to overwrite. When I think "this is too short, I need a little extra meat here" I'm overdoing it. When I say "I'll keep it extra simple and if the times come I improvise some things to fill in the blanks" I have to improvise nothing and the session is in about 4h, while my common one shots become 3 shots of 12h sessions ¯_(ツ)_/¯