It occurs to me that it seems playing one side of a 33.3 takes about 20, 25 minutes.
About how long did the old 45s and 78s play, on one side?
It depends on what the diameter is for the record, among a whole host of other things (absence or inclusion of needle lead-in/lead-out, true play speed, number of grooves). On a typical ten inch 78, it's around 3 1/2 minutes. Orchestral music was typically on twelve inch 78s, and their play duration is subsequently longer. The "hotter" stuff typically ended up on the smaller records. There are some pretty bizarre record sizes out there, up into the twenties of inches, if I'm not misaken.
I only own a few 45s, and only for sentimental purposes (they were given to me). I haven't played on in a while, so I can't give you a solid answer. If I had to hazard a guess, I would say they're around the same length as a 78.
Bear in mind that there are different diameter 33s as well. I have 33s that are only ten inches in diameter, and as such don't play near as long as the standard twelve inch size.
The last ten inch 33 I picked up would no doubt make the grasswipe primitive drool with envy, had she been able to purchase it for what I did, and see what the completed listing prices go for on her beloved Ebay (4000% profit).