Never

I've come to the conclusion that one should never revisit a favorite TV show from childhood. All the bad acting, writing and special effects that you could ignore when you're 12 become magnified in adulthood.
When I was a kid I loved a show that was only on for a couple of years. That show was called "Project UFO" supposedly based upon the US Air Force's Project Blue Book investigations of the 60s and early 70s. I loved it, it was edgy and the stories were true to life.
As an adult...good god what in the heck was I thinking?? It was produced by Jack Webb, of "Dragnet" and "Adam-12" fame and like those shows the dialogue in "Project UFO" was stilted and so badly acted.

The problem I seem to be having with pretty much all of Jack Webb's work, "Dragnet(1960s)", "Emergency", "Adam-12" and "Project UFO" is they are a product of a time where most of the TV producers grew up and were trained in the time of radio dramas, Dragnet being an adaptation of an old 1940s era radio show, and a 1950sera TV show and it shows in their work. The actors walk on screen say their lines and walk off. The sets look worse than the displays at Ikea.