haha ok, just wondering if you can stretch the fabric or something that'll mess up the light dispersion
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I don't think that will be an issue. Photography studios leave the umbrellas up nearly all the time (at least during business hours...not sure if they close them at the end of the day). The fabric isn't usually the thing that goes--instead, the mechanical pieces that provide tension to the fabric wear out. However, I'd say that constant opening and closing might cause one of those pieces to fail sooner than if it was tensioned all the time (that's only a theory, though, with no observation to back it up).