I have a G9 I bought 2 years ago and it intermittently cuts out while gaming, just started at random. Doubtful the g9 has a lifetime warranty,
In my experience the cords on the G9 and G9x aren't great, and they tend to start fraying where it connects into the mouse. That might be the cause of your issue. IIRC, it has a 3 year warranty so there's a good chance you'll be able to get a replacement.
Aside from the cord, the G9x is pretty much my favorite mouse (gaming and otherwise) ever. I bought a spare the other day since it looks like it's being phased out.