What age range did you use a puddle jumper?

We currently have one for my almost 4 year old to use in the pool. We have put it on the 1.5 year old and she's iffy on it and a little small for it, but it would work ok and I think she would enjoy a little more freedom in the pool plus get used to me not holding her so close in the water.

So I'm wondering if I should buy a second one now, or if the almost 4 year old is about to outgrow hers and thereis something else I should get for her and pass hers down.

She's taken swim lessons but isn't close to being able to swim independently, and I sometimes bring both to the pool by myself so I feel better with at least one in a floatie. Of course we still stay in the shallow end and I keep them close to me, floatie or not.