They hold up well. I personally turn the garment inside out or place in a netted wash bag. Use a different color of bobbin thread just for the fringe and it makes clipping the right threads easier.
I have not done any recent fringe designs but the ones I have on my bathroom towels have held up really well. Several years old now and starting to look a little flat but have not come apart.
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I should wish to know if those fringe designs are washable, does anybody has try?