How long does it take for the yellow dot to go idle?

[rickywatson]

The other night I could swear my friends dot went idle around 15 minutes of no conversation...but another friends dot never goes idle, yet it is on all day...and he says that I am the only one he talks to...is that possible? If we haven't talked in hours, wouldn't it be idle

[mighty]

It would be idle but not sure. I am also looking a definite answer of this.