Well, instead of thinking about it in terms of years, try to think about it in terms of drawings.
104 drawings a year (est) * 20 = 2,080 drawings
Sounds like a lot right? But in the case of Powerball, let's try the math assuming one ticket per drawing. Obviously the matrix has changed over 20 years but cost and odds aside we can make a reasonable generalization (i.e. all things held constant).
(175,223,509/175,223,510)^2080 = 0.9999881441
That gives us the probability that you lose 2,080 drawings without a win.
So we simply subtract that from 1 to get the probability of winning at least once.
1 - 0.9999881441 = 0.00001186 (0.00118559%)
More than odds of 1 in 84,000 that your set will show up any time in 20 years worth of drawings. So it's not even likely or close to likely.
Obviously, nobody needs reminders about what a stretch it is to win the lottery or come close to it. But the fact of the matter is that you will only win by pure luck, regardless of what numbers you choose or how you choose them. Every combination has the same chance of occurring. You can play one set for 20 years or a different set for 20 years and still have the same probability of winning. That's why I don't get hung up on "missing out." It's just a fallacy of human nature to feel this way, and probably the reason lotteries are so successful. You might feel like you've lost your chance, but like I mentioned earlier: there's no law that says you have to win with a specific set or cannot win with a specific set (or any for that matter). You wouldn't feel like you missed out if you hadn't played your numbers but instead played a substitute set that won, right? You would feel like you would've missed out if you had played your original numbers. A little paradoxical if you think about it. It's just unlikely that any specific set shows up as a winning combination.
If the chances of winning the jackpot are so slim, why play when the jackpot is so small? Your chances never change, but the potential payoff does.
If a crystal ball showed you the future of the rest of your life, and in that future you will never win a jackpot, would you still play?
P&L % = Total Win($)/Total Wager($) - 1