It is but it is not black and white. 90% charges for a week is pushing things. It would be proportionally worse of course at 50% state of charge. I would get a 10 amp portable solar panel and cook the batteries after generator shutdown. A morning charge then 5 hours of sun may produce 40 surplus amp hours in a larger say 400 amp hour bank - during that last 10%. Yes, decreasing the missing ampere hours from 90% SOC to 95% SOC does make a difference. A Harbor Freight 2 cycle generator and 29 amp Megawatt would also work great depending on the noise. Let the little generator run until it runs out of fuel @ 14.4 volts setting on the Megawatt. Absolute Scrooge fuel use. And no attention to anything - put the generator and Megawatt away after it plays possum.
I institute "light use days". Charge then shut off all loads and let the panels top things off. Doesn't mean the refrigerator, but lights and other accessories are neutered.