I'm really not a hypocrit.
When my boys were young, I would let them pick out one box of cereal each. Naturally, they took the box that offered a toy of some sort. Because it's natural for children to take the toy and leave the cereal, then go off to another box and toy. I made the rule that they couldn't open another box if there was still cereal left in the first box. That way, no cereal went to waste.
Now, I'm in the same situation. No, I didn't buy a box of cereal for a toy. The last time I went to Costco, I bought huge boxes of Cheerios and Corn Flakes. I enjoy Cheerios and finished them very quickly. Then I started on the Corn Flakes. I had forgotten that I really didn't care for Corn Flakes. Now, I have to eat them until they're gone.
I think they will last for a very long time. And, I can't open another box until they're gone. But, I never made the rule that you can't have toast, waffles, bagels etc. so I'm varying my menu - cereal one day, toast the next, or maybe bagels the day after. I should be done with that cereal in about a month.
But at least I haven't violated my own rule.