I've used this for three years now to start my seedlings. I start in March with flower seedlings, started in house, and continue till late May,in house. It then goes outside for rest of summer as I then use it to hold garden tools,pots and such until October.
It's still working like a charm though I do zip tie the shelves each year when it goes outside. I also use sandbags on the bottom frame to hold it up. Still zips up with no tears. Worth every penny.