Years ago I once made the mistake of leaving VWP to soak overnight in a plastic pressure barrel. It took a major effort to get it free of the chlorine smell afterwards because plastic is porous and the damn stuff had soaked in.
I'm surprised as I use plastic FVs and have left them full of SVP for 2 or 3 days many times with no problems. For rinsing I hold the FV upside down in the garden and spray the inside with cold water from a hosepipe for a few minutes, going round and round the sides and base, and I've never noticed a smell of chlorine afterwards. Maybe a pressure barrel would be harder to do that with as it's heavier than a FV and would be difficult to hold upside down in one hand while doing the hosepipe thing with the other.