I use low fees if I'm just putting away some bitcoins into cold storage or transferring to other wallets. By low I mean 100-200 Satoshis/byte, never under 100. They usually confirm within 24h so I suppose I could go lower if I wanted to but waiting weeks seems silly.
I think low fees it too good, when we talk about someone who doesn't care about the speed of confirmations of his transactions, Like me. but in my case, I am obligated to use a high fees, because xapo set a regular fees which they controled by xapo not by me. Furthermore, these fees are too high.