I think it really depends for each horse! Typically I like to take my time particularly with a horse who is very careful - the more patient you can be the better! I would say when a horse is consistently jumping well at one height, day to day and week to week, you’re probably ready to move up. Be mindful of the venue that you are moving up at, it’s important not to overface your horse! I’d also move up the second day of jumping at a new venue rather than walking straight into a bigger class.