A track meet? A long jog through Marathon? A Marathon race?

A Marathon².

Someone with too much time on their hands

Maybe a marathon of Marathon.

I believe it's the same as having several rounds of beer: session.

go through it without killing anything other than the mission requirements and then it's a marathon.

Thermopylae achievement?

Metathon

I call it a wet dream.

Tempting fate with the carpal tunnel gods.

I would derive that you would be doing:

d/dx [f(m(d(i)))] = f ' (m(d(i))) * m ' (d(i)) * d ' (i)

where: playing the marathon trilogy= f(m(d(i)))
marathon = m
durandal = d
infinity = i

Oh oh! i know! Run a Marathon pfhor Marathon!

Maybe if it benefited AIDS research I'd actually take the time to sit down and beat all three.