I believe in age appropriate wear, but that's for ME - a personal choice. Otherwise: ditto on situation appropriate. Oh, and I still wear Chucks.
At some point, I realized that I had many many free T-shirts, concert t-shirts, jerseys, etc. that made me look like I was perpetually 19 (independent of passing or being trans). Nothing I wore was fitted or age appropriate, and while it was comfortable, it didn't look like anything - probably because I wasn't interested in having my body visible anyway.
Eventually, I reached a point where I realized that I coud dress comfortably and still look less like a slob and also look more my age. I didn't throw out every t-shirt I owned; however, it is hard to wear an ironic t-shirt on the other side of 30 and have it still be ironic. So I saved the stuff I really cared about, and I wear it in occasion appropriate ways. Once I started transitioning, though, it was harder to wear all that unisex stuff and still get read correctly. Since being read in an age-appropriate way is my hurdle (I pass well as male, but way too young), I'm more sensitive about wearing t-shirts and college-kid clothes. Plus I like wearing real men's clothes, and I see that my "style" before wasn't a style at all. I'm never gonna be that fashionable dude, but I'm not as attached to that t-shirt/jeans look. I suspect that once being read correctly is less of an issue, I'll continue to wear some of my favourite old stuff, but I won't feel driven to replace it with something similar as it all disintegrates.