Is there some rule regarding this?

I think the "rule" is every 8 hours, I changed when I see the need

when it breaks or i can hear it popping through fabric

I wouldn't say there is a specific rule, but I change mine whenever I start having issues; usually the first thing I do if I start with the thread breaking or any other problem.

I use a new needle with every new large project. I wouldn't change a needle every tablerunner,placemat, but with every lap sized or larger quilt. I also change needles from piecing to quilting as well.

Like my rotary blade, probably not often enough, until there is an obvious problem :roll: :D:D:D

When it breaks!! And it hardly ever does.

When I feel I really need to, which is not often enough. :-D

I change at least every 6 hours of sewing time, or sometimes less....avoids many problems!

I can tell the difference in sound on the machine when the needle gets dull (I just heard that sound again). So time to change the needle.