I had a really cheap one that lasted 3 years for me, I wasn't sure how I'd like it in a planter so didn't want to spend a lot. It would have lasted longer but the vines I plant get very top heavy and our high winds often blow that planter over. The shorter planters even can get blown over so now I put 3-5 bricks at the bottom of each. But the tall vine planter still gets blown over, and this past summer the way I tried to stop it actually ripped the plastic planter apart, so it just hung lopsided by a chain to the top of the garage until I could find a big enough planter, and that bent it and weakened some of the poles. I did shorten by getting rid of the damaged sections, so I might find a use for it next summer.
But I also bought 4 very sturdy flat metal trellises this past fall for next year that are 10" wide, and I plan on putting all 4 into the planter to form a square for the vines to climb. They're much sturdier than the tubed obelisk I had and I think they'll hold up for many years, long enough that if they should rust I can paint them with Rustoleum. Hopefully... at least that's the plan so they last longer.
