I replace mine daily.
There is no Use By date on underwear ¬.¬
I'd suggest replacing your girlfriend.
just recently got rid of a pair that must have been hanging around for 10yrs....were falling to pieces though. they just seem to last for ages, now socks are a different matter i buy about 10 pairs a month where do they go??
I throw mine away when i start to get holes in them.
I throw mine away when i start to get holes in them.