Can anyone tell me if muscle recovery times decrease as the body becomes more accustomed to running at different intervals and distances? I have seen some posts that say it takes 20 hours for recovery and some that say 24. Can anyone please clarify?

Excluding the first week or so of exercise, recovery rates for any given type of workout should stay basically the same assuming you are not varying your nutrition, sleep, or the kind of workout you did the day before. Keep in mind that muscles recover in a manner which follows the stress adaptation curve. If you break down a muscle from baseline strength and it takes two days to recover and supercompensate to above baseline, that same muscle will take longer (3 days) to recover if you already broke it down the day before, since it is already below baseline.