My Mum bought us a trampoline when I was ~ 7, my sister would have been ~ and my brother ~1. We used that trampoline on and off over then next 9 years, and my youngest sister also used it. Mum only sold it when they moved and my youngest sister was ~13. So it got about 22 years use out of it!
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Now I know our family is a bit weird in that there is a 16 yr age gap between 'the baby' and me, but I honestly think that a trampoline is a good investment.
As teens, we used to sit on the trampoline and talk with our friends. A quiet place with no evesdropping parents around.
I grew up in NZ. And although it doesn't get as hot as it does in Aussie, I distinctly remember spending many summer days with the sprinkler under the trampoline jumping around in our swim suits. Or setting up the hose to spray us as we jumped.