Tagalog translation: vent-a-ton, maratón de ventas
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Explanation: No way I can turn this around, unless you go for the coinage "patubili" (which runs the risk of ambiguity if pronounced as "malumanay" - accent on the second to the last syllable). Your etymology is also a bit off - "athon" in this sense comes from Marathon, which is a Greek place name that denotes the site of a famous battle. The Greeks won against the invading Persians and sent the news home through a runner who collapsed upon reaching town with the good news - he had run 41.6 km., I believe, which is the distance for a marathon today.
Note that this athletic feat is not to be confused with "decathlon", which was the Olympic event featuring a total of 10 comptetitions (deca-).