They are legit, however Shipping can take longer than that. There are a few posts on here of 0SZ having issues with HongKong Post Office and then with China Post which they switched to.
Logically, those issues should also effect other retailers based in China. Although I don't know if that stands true.
ShopTemp say 2-5 Weeks to cover themselves. So 0SZ will probably take around 2 weeks, but in some cases may take upto 5 weeks.