My littlest DD has the record for repeating LTS levels ... 2 years in a level that some kids whip through in a month or two. However, that's fine by us; she's enjoying herself, and doing well. We just let her go at her own pace. Every kid develops differently, and has different physical coordination plateaus/gains. Suddenly, this summer, she's starting to move faster and progress faster ... and we're seeing more progress. But, whatever she does is fine ... as long as she's enjoying herself!
IF it makes you feel better, my other child spent quite a bit of time at a particular LTS level, and is now well beyond the level of virtually everyone that whipped through the level (competitive track). Two reasons. The coordination to do a particular level wasn't there yet, and, also, the coach considered that level to be important and wanted to fully master the skill. It's paid off later ... as it was one that focussed one edges, turns, stroking and that, plus, the introduction to single jumps.