Stray: main story about 6.5 hours; story with some extras about 6.9 hours; 100% completion about 13 hours. These are IGDB player-submitted averages from 19 submissions, not a deadline or a prediction of your pace.
Source: IGDB player submissions
Community playtime data is not available for Stray yet.
Game Tales keeps what happened between you and a game in one Tale you can keep building.