I'm embarassed to admit this, but ... I've had a roller of paint wrapped in clingfilm for over three months! (the rain put off the outside job)
It's still soft and ready to go.
I've been clingfilming brushes for years ... I don't know why I didn't think of using it to line the trays before now. Ah well, better now than never.
I'm guilty of wrapping paintbrushes "for use later" ... only to come across them weeks later as hard as wood. But, if it's emulsion, just soak them in hot soapy water and they come good.