Is it normal to fill up the grey water tank this fast?

I've seen people fill a 30 gallon grey in a few days. Personally DW and I have often gone 10 days and just barely used 30 gallon grey and half filled the 30 gallon black tank. We can go about 6 days before filling the 35 gallon fresh tank.

We do showers every other day, dishes once/day or even less often if we are careful.

but if your not carefull, well tanks fill up fast