I had fun working this out:
My boyfriend and I had spent 247 hours solid together, not including time spent sleeping or showering, when he told me about his feelings for me. I didn't think that I felt the same at the time he told me, but realised I really did by the next evening.
Inbetween this there were Facebook messages and MSN conversations.
In total this spanned 6.5 months. Although we spent one day solid together, then three days solid with no sleep, then another 3 days solid with no sleep, then 6 days of him staying with me (with sleep hah) before he told me. Since then we've been together 70-80% of the time I'd say.
We talked for hours, walked everywhere exploring cities, went to concerts, galleries and theatre... Yeah. It was pretty obvious we really really enjoyed each other's company. Most fun of my lifetime so far (which isn't very long, but I've had so many really fun experiences).