I didn't start allstar until Uni so I was 18, I competed up until I was 21 when my body basically said enough is enough (I used to do competitive gymnastics so wasn't exactly new new). Older members of my team who didn't have any previous tumbling experience did struggle with it but if they put in the work, on average they got to about level 2/3 tumbling within a year or 2. I'm in the UK where we don't have an upper limit for senior as long as one of the members of the team is under 17. If everyone is 17+ then you become an open senior team which is what all our unis compete in - you can be whatever level you want for open senior: 1,2,3,4,4.2,5,6 for full routines or group stunts.