@silkybunny I purchased my very first pair of lululemon leggings (plain black low-rise Wunder Unders in a 4) when I weighed about 113 lbs and did a ton of running. I still have this pair today and wear them despite weighting about 137 now, thicker legs and thicker everything. I also own a purple crop pair of WU's and a pair of WU's made with a rulu fabric that is a herringbone pattern...currently wearing as I am typing. All three of these pairs were purchased in 2011. I used to own some luxtreme running tights as well but ended up growing out of them/not running in them anymore that I sold them.
Since then, any other pair of leggings I have purchased whether they were Athleta, Victorias Secret sport, Fabletics, FourAthletics, Fleo, Born Primitive, Vuori have not even come close to matching the quality nor accomodating my change in size.
I recently purchased two pairs of Align leggings the other day going up to a size 6 (because I was about to grow out of my 4 so why not) - and although they were soft, I was incredibly disappointed in how they were constantly falling down and not staying in place. They already started to pill between the legs after 1 wash and are way too delicate for me to use my fabric shaver on.. My regular luon leggings didn't start pilling for several years, but I can take a fabric shaver to those in confidence because the fabric is like freakin iron.
I've heard that the fabric quality has changed a bit over the years though - the original luon got changed to two versions (luon which is apparently lighter, and full-on-luon which is apparently slightly thicker? or the same?). But I have exchanged my aligns in hopes of getting another pair of Wunder Unders since that cut has been a dream. And, heading into pregnancy shortly most of my friends have said that the high-rise wunder unders have been the BEST pants going through maternity and beyond.