In the 1960s Peg Bracken's "I Hate to Cook Book," was my entree to the world of (and to the term), "planned overs." I was a full time student, with a part time job and newly married. We had a VERY tight budget and (even then) student debt. My then husband held a full time job, and a part time job AND we managed a 12 unit apartment building in return for reduced rent. He also cooked and shared chores like laundry. I didn't hate to cook, but we had little time and needed all the planning and short cuts that we could find, without relying upon expensive (for us) ingredients like prepared soups, mixes, etc.
These days, I can buy better fresh ingredients but I "cook big" and freeze entrees, homemade stocks, and pasta sauce for the next few weeks. That means that I eat better as a single than most families eat. And, you will have to pry my 7 qt. slow cooker from my cold dead hands. (NOT a Crockpot; those boil everything, even when set on low!) I use that to make large batches of chicken stock to reduce and freeze. I also have a 3 qt and a 1.5 qt, and those two are often both in use at the same time when I am cooking ahead.