I originally used the Sterilite 27 Quart Storage Boxes to transport my plants from the garage (dormancy) to outside in spring. Unload the plants and take the boxes back to the garage. I did this for around 3 years with the same boxes.
Last year I decided to leave the plants in the Sterilite 27 Quart Storage Boxes all summer. This was great because I did not have to water near as much since the boxes filled up with water. I did have holes drilled in the boxes around half way up so they did not fill up completely.
As most know that the sun destroys these boxes after 1 summer in the sun. That's why I asked and am now using the cement trays.
I read where some other people had painted Sterilite and other boxes and they held up to the suns rays then. My only concern with painting the boxes would be is there any chemicals that would be released from the trays when there is a few inches of water in them long term and then enter the soil of the pots, and cause any adverse effects on the plants??