Generally the rule is no more than 10 minutes a time for a weighted hoop, especially not at the beginning.
You actually get exactly the same level of calorie burn and just as good (if not better as you can move far more and faster) cardio workout with a lightweight dance hoop ie one like this.
I had a weighted knobbly hoop when I first started hooping four years ago, but quickly ditched it for a dance one, you cant do tricks with a weighted hoop , I now have five, all different weights and sizes .
You would be much better with a lighter hoop, the weighted knobbly ones just seem like such an odd concept when you use a proper one.
They don't come apart but you can get travel ones that fold like this.
Using a dance hoop you can exercise so much more than your abs and it is a much better all round workout, when people talk about the huge calorie burn you can get from hooping, they are talking about whole body dance hooping and really getting your body moving, spinning a very heavy hoop round your waist has a very low burn and only works a limited set of muscles.