For me, the rule is a bit different. I am willing to spend the time needed *as long as I enjoy* the prepping and cooking. For example, yesterday I made a traditional bowl of red (around here they often will name it chili con carne, but that's definitely not the same), which took me quite some time. The eating itself was done all too quickly, sadly.
To me cooking is a nice moment to recuperate from whatever I've been doing that day. That's why I find it so important to only do whatever I enjoy in the kitchen. Especially when I still had my business that was really important to me. As soon as it starts to resemble work, I will ask my wife to take over. She's doesn't like cooking though, so she's glad that doesn't happen all that often.