When to stop using sleep sack?

Honestly even when baby’s attending IFC, they recommend to start letting go swaddle, but i would just still use swaddle or sleep sack when he’s napping or sleeping at night so he can have longer sleep. Cause he tend to startle alot when not using which will wake him up

My baby doesn't like to be swaddle.So I use sleeping sack.Once she knows how to flip,I remove sleeping sack. I didn't had any issue to get her to sleep without sleeping sack.