Underwear

Okay heres a question that popped up while pondering on the way home from school drop off this morning, how often do you get rid off underwear and what criteria do you use to determine when to toss them? I feel like I could be weird, I have like 4 pairs of sexy panties that were obviously well made and I've had them for year's (with good care theres no stains, holes, or anything). But then I've tossed underwear that are a year or less old because they would get holes, thread coming loose, wrecked elastics, etc just from being cheaply made underwear. So my own criteria is that I only throw them out of they're falling apart. Is this kinda gross or? Like I mean I have excellent wash routines thanks to being a mum, so I don't see it as a problem? But wonder if this is common for us ladies? My husband gets new underwear every 6 months ish being a tradie his get worn out quiet quickly lol.