I don't see why the sports almanac would quickly become useless? If the implication is that it would be a result of you winning large sums and potentially altering betting lines, I can see the size of the winnings going down, sure, but I don't know that the actual results themselves would change? Is me going back in time and placing a bet on the Super Bowl winner five years ago, and then doing the same every season thereafter, somehow going to butterfly effect and cause the Patriots to not win last year? I mean, take all the personal implications of the same dude picking the winner every year out of it, but I fail to see how the almanac becomes worthless that quickly. I could see a large number of years potentially beginning to diverge just because of RNG, but unless I have some kind of connection to the sporting world, I just don't get how it becomes worthless due to my actions. Maybe someone can explain?
Assuming you had no other insider knowledge but the almanac, and didn't care about people questioning your luck, you could still make thousands of bets in a few month span. I'm sure you could easily get up into the millions with that many smaller bets, and drop a few larger sums on some of the big name events that people already bet millions on. Sure, I'd rather just have a winning powerball number that had previously not had a winner, but if I only had sports betting, I could make more than enough pretty quickly I'm sure. Avoiding suspicion would be the only really difficult part.