Owlboy: main story about 8.2 hours; story with some extras about 9.6 hours; 100% completion about 11.8 hours. These are IGDB player-submitted averages from 2 submissions, not a deadline or a prediction of your pace.
Source: IGDB player submissions
Community playtime data is not available for Owlboy yet.
Game Tales keeps what happened between you and a game in one Tale you can keep building.