Buy it for life: Durable, Quality, Practical

Jockey makes great underwear, their return policy is by far the most generous I've seen and it lasts for years. For a size small, they fit a bit better than Duluth Trading Co and Costco but I tend to wear their boxer briefs

You might try Exofficio. While I can't speak on their traditional boxers or briefs, their boxer-briefs are great imo. They're comfortable and breathable.

And durable--I've had several for over 6 years and the only thing showing wear is the waistband--buy this is definitely a reflection on me because I got lazy and gained weight.

I originally heard of them from a reddit bifl thread, where I also discovered Darn Tough socks. I vouch for both brands and use them exclusively.

My personal favorite are Duluth Trading Buck Naked. I’ve had a few pair have the elastic waistband start to stretch to a point things don’t stay put. But those are ones I’ve had for about 10 years. Never had any other part wear out. Keeps me cool, since I run hot. They have both boxers and boxer briefs (and maybe briefs). They are somewhat expensive at ~$22/each, but you can wait for sales to get them about $16/each.

Not regular boxes, but I've been using the Costco Champion boxer briefs for years. Super comfy and durable. They don't get all stretched out like other brands. Highly recommend them.