Seniorboy is fussy and likes his food varied from day to day/week to week so I generally have about 8 or 9 partially opened boxes of different brands in the house. (His food takes up more of the kitchen pound for pound than the rest of the family.)
He also gets some cold meat or similar at lunchtime - only at one meal a day as a treat because of the nutritional content.
His main foible though is that he doesn't like fishy flavoured food. I'd, from experience, keep an eye on yours and if you're going to buy multipacks for the better price, don't go for one that's only fish or only meat. Just in case.
My main recommendation would be to keep the amounts fairly modest and go instead (if you can, work permitting) for a frequent turnover. They like it fresh.