I bought a rocker for my #1 and used it for #2 too. It’s useful especially if baby has reflux issue, you can put your baby into the rocker to keep him/her upright after milk feeds. But of course, don’t on the movement 😂
The one I bought is solely just a rocker though, so your concerns are right that it can’t be used for too long. Maybe you can consider something like this instead: https://welovesupermom.com/products/97-510803-Lucky-Baby-Infant-to-Toddler-Rocker-Vibration-Music-Lion
It’s suitable for infant to toddler. When they are older, can use it like a chair. Price is quite affordable also
Ann