I am not as experienced on machines as you guys sound like, i have the odd couple of quid in a pub but i have heard this "Dropping" theory but i have never seen any pattern in any machine. I could be in my local Friday, Saturday and Sunday where the machine gets battered all day and the most anyone wins on the £40JP is about £7-£10. Then you could go in the next weekend and its paying out like nobodys business.
I suppose you could use the argument that there may be people playing during the week but whenever i go in for midweek football nobody ever plays them during the week