I didn't go swimming much so I had only one swimsuit which I must have had for at least 10 years or more. It was a navy blue speedo and still fit so I figured why throw it away. Most times when I needed a swimsuit it was to go to a waterpark and I went to a few every year. I did notice my last couple of years wearing it that more people began to look at me in it. I figured it was because it was a speedo and revealed more skin than the swim trunks guys were mostly wearing. My last time wearing them I went to use the washroom and went past a mirror and noticed something about them. The whole back side of them was sheer when I wore them. When they were off you couldn't tell but I guess when the fabric was stretched tight across my ass it made it extremely thin and revealing. You could see all details of my ass including my cheeks, ass crack and even part of my balls. I guess with the age of the suit and all the waterslides I had gone down it wore the fabric extremely thin without it actually putting a hole in it. I guess it didn't help with me not washing them following the care instructions possibly causing them to wear thin quicker. The front side had no wear, and since I never really see myself from behind, I didn't know the suit had any issues so I was just unknowingly exposing my ass to everyone. I don't even know when exactly the material became so thin that the exposing of my ass began to occur but I am guessing at least 2 years at minimum.