I'd say if this is this combo you eat all the time, thats not a high enough protein ratio in your diet. For example at the moment I am actually eating a bag of peanuts. Per 100g there is 24.5g protein, 53.0g of fat and 7.1g of carbs. That is 29% protein, but if you add bananas, pure carbs, the figure goes much lower depending.
At the same time you wouldn't wanna just eat peanuts without bananas because there are basically no carbs which isn't very good for bulking, though maybe cutting.
Also, bear in mind all nuts aren't blessed with the protein content that peanuts have, some are almost totally made up of fat.
My advice would be to drink skimmed milk as a snack. Simple. Its about 35% protein and quite low in fat.