Yes, there is the "between each project" but one can go from a table runner to a king size quilt ... and a lot also depends on the type of piecing you are doing - little pieces (lots of seams), but pieces, paper piecing??
Other teachers will tell you after X hours of sewing, but of course the rules above will still differ to a degree what can be done in X hours. And the type of fabric, I think batiks are rougher on needles than a more open woven fabric. I'm not sure if heavy starch makes any difference or not - I guess it's possible.
So instead of counting hours and taking all of the variables into consideration ....
... I use my ear. I can hear the different sound an old needle makes as it pierces the fabric (soft thunk or pop) compared to a new needle (no sound or a very soft pfft).