We have acres fenced in, with t-posts. Some were put in 15 years ago. I think how well they hold has a lot to do with what type of soil they're used in. We have very heavy clay here. In other, looser soils, I'm sure they wouldn't perform nearly as well. I've watched a big ram scratching himself against them repeatedly, when his wool was really long, without dislodging them. I think it just depends on where you live.