You can accurately calculate a slot machines payback after 10million pulls.
Theoretically if you could wait it out this long you would get anywhere from 85% - 96% payback regardless of the machine you played as that is what is legislated in Nevada.

If you can afford to play at this level you might as well buy the casino.

If you follow this theory and play the Pick 6 out of 49 style lottos you can guarentee yourself a positve payback by playing every number combination once the jackpot builds to 44mm or greater. I believe that you need 22.8mm as your seed investment.

There are however a few gotchas. First if there is a second top prize winner you will lose 12.5mm .... sometimes there are 3 or more winners so this loss could grow wider. Secondly you will have to pay taxes. You will have to show documentation for the 22.8mm of gaming risk for this to help offset the taxable amount to remain positive, your winnings could also be disqualified for "systematic gaming" which is illegal in most powerball states. The Final problem becomes into actually getting someone to scan each of the tickets in. Asumming you have 1 week from lotto to lotto to get this done, and you could do it error free which is an amazing stat in iteself you would need something like 187 clerks entering tickets in 24hrs a day non-stop just to get each of them entered.

Systematic gaming is the disqualification of results where you find a way to beat the odds in a non-cheating way. This law was introduced in the early days of scratch and win. The retailers were delivered a box of S&W tickets. Within the box three tickets were elgiable for top prizes. Overall each box created a postive revenue for the retailer. At some point someone figured out that the three winning tickets were always the same three winning tickets and consipered with other reatailers to cherry pick these out the box. Either for personal gain or simply to be shread to further increase the retail value of the box.