I spend quite a lot of time working near these machines during the week on and off.
What I have seen is the machines are indeed at idol for long periods through the day on a weekday.
I see the odd guy or guys who are obviously pinheads and play 3 or 4 game on every machine but mainly its a passing family or couple that just have 1 game on one machine then move on and a funny enough a lot of the time leave a credit on the machine from the match without even realising it. My guess would be an average of 1 game per half hour for each machine during a weekday.