It takes a while. Usually they'll promote you to Senior Team Lead before ETL to see how you balance LOD shifts with responsibilities in your workcenter, and how well you deal with high scope situations.
To expedite the process, be on your A game 100% of the time. Go above and beyond in your workcenter and others. Be a real leader, not just a glorified TM. Take partners with TLs of other workcenters and (even better) ETLs. And make your ETL and STL believe in you as much as possible, as once you're a senior, they'll be the ones pitching you to the DTL for the promotion once you've been in role for 18 months.