Although obviously everyone is different, I think it also depends on what your normal "range" is, if you're used to higher levels what may seem like a hypos to you could be perfectly normal for someone else. Over a longer period of time it's certainly possible to re-educate your body to get used to lower levels, up to a point.
Below 5 is when I start to get nervous, and with no awareness of hypos that's understandable I think? But I don't like to be over 7 either, that being the point at which vascular damage starts. Feels like a tightrope sometimes!