I discovered Valby Croquis almost by accident.
I attend group drawing sessions there multiple times a week. Some sessions are typical group sessions with poses at various durations, from 1 minute to 20 minutes. In other sessions, the model holds a single pose for the entire evening (usually for 20 minutes at a time, with 10 minute breaks). I attempted adding color during some of the latter type of sessions.
Already after my first visit, I knew I could expect to be come a regular!