Sounds like your filter is working and behaving properly

If you have a small amount of debris getting into the pool, you an go for months without having to backwash. A few years a go I wrote up the Use and Care directions found in this sticky.

The benefit to backwashing before the gauge rises ~8 psi, is that you can get a more complete/ thorough cleaning. If you go this route, you'll need to add closer to 90% of the recommended DE when you recharge the grids.

I will always recommend taking a DE filter apart and manually cleaning it at least once a year - it lets you check what's going on in there