In your hypothetical, yes, you are correct in saying that if your opponent is unable to perfectly identify when you're bluffing and when you're holding the nuts, they will lose EV (Expected Value) over time. However, it's worth mentioning that this is based on a very simplified assumption of the game that isn't representative of the depth and complexity of real poker scenarios.
In this scenario, pot odds are indeed 1:1 or 50%, as the opponent would have to call 100 to win a pot of 200 (your all-in 100 + the initial pot 100). However, let's discuss the situation from the perspective of GTO (Game Theory Optimal) play.
From the GTO perspective, it's about being unexploitable and making the most +EV decision in the long run. GTO doesn't always mean calling correctly every time, it means making the decision that gives your opponent the least benefit. If you are perfectly balanced with your bluff/value ratios, your opponent cannot exploit you.
Let's assume your opponent knows you're 50% value betting and 50% bluffing. Given the pot odds of 50%, they should theoretically call every time. But if they know you're only bluffing 30% of the time, even though the pot odds are the same, the EV of a call decreases.
However, in real poker, your opponent won't know your exact frequencies. GTO play aims to mix value hands and bluffs in such a way that makes it impossible for opponents to exploit your play, given the size of the bet.
The amount of times you should bluff with an all-in on the river, or any street for that matter, can depend on a lot of factors. These can include things like the size of the pot, the cards on the board, your opponent's likely range, your own perceived range, your table image, etc.
A common strategy is to base your bluffing frequency on your value-betting frequency and the pot odds your bet is offering to your opponent. This can be mathematically calculated using the formula:
Bluffs = (Pot Odds / (1 - Pot Odds)) * Value bets
So, for a simplified example, if you're betting pot size (giving your opponent 2:1 odds), and you have 30 value hands, your number of bluff hands should be (1/2) * 30 = 15 hands.
Remember, in real play, things will be far more complex and variable than these simple examples. But these principles provide a starting point for understanding GTO strategy. The aim is to make your decision frequencies balanced and hard to exploit.
Finally, pot odds don't necessarily decrease in importance as you progress through streets. Instead, as the hand progresses and more information is revealed, you must constantly update your understanding of the situation, and adjust your strategy accordingly. Pot odds are always an important factor in deciding whether a call is profitable in the long run.
Some articles on bluff frequency:
https://upswingpoker.com/what-is-bluff-to-value-ratio/
https://www.runitonce.com/nlhe/calcu...-overbluffing/ <- Shaun Pauwels has a good note here for some quick calculations you can refer too similar to quick pot odds calculation.