For anyone citing the former playing of 3 day tests IIRC, I remember 3-day tests being criticised in Wisden in 1926 (vs. Aus) and 1935 (vs. SA) for obvious reasons. In both series, only a single test produced a result: in 1926, it was the final, timeless test; in 1935, the Lord's pitch turned from very early on. Newsreels also carried criticism of the 3-day rule in 1935 as well.
Also, five-day tests being a compromise between timeless and three-day tests is not true. Aus-Eng tests in England were four days in 1930, 34 and 38 (though in the first, the series was decided at final timeless test, 38 was drawn). Other countries got three days. Post-war, 47 vs. S. Africa had 4 days, 48 vs. Aus had 5 days, and 49 against NZ 3 days, with all tests being drawn; a clear pattern of fewer days for weaker teams, and keep in mind over rates were probably much higher at least before WWII. From 1950 onwards, all tests were 5 days long in England. In Aus, tests were timeless before WWII (ignoring pre-WWI), and 6 days straight away after it (though with 5 hour days) until the late 60s (I think). Other places may have varied again, but there was a pattern of the shorter tests being scheduled against NZ weaker sides, and longer ones between sides consider more even.