When I was starting out and lessons would introduce exercises, riffs, patterns, etc. [u]my own[/u] rule of thumb for moving on to the next lesson was when I could play the current one at speed three times in a row without error and with clear sounding notes.

None the less, some things, particularly songs and exercises, need to be/should be reviewed frequently even after 'moving on.' Exercises especially can be incorporated into daily practice/warmup sessions with ever increasing speed and/or picking, e.g., quarter notes to eighth notes to sixteenths. Technique ('chops') can always be improved. IMO.

Good luck, have fun