Stolen bases are overrated because over the course of the season, they just do not add that much run value to the team's overall offense. That statement is supported by data. As far as stolen bases having a big impact on a single game, that is true. But so do the caught stealings. No one tends to remember the momentum killing caught stealing, because it's not as obvious. That erases the big impact of a stolen base from a previous game.
Momentum can last several games, or it can last as little as a 1/2 inning. The point is that it has no predictive value. It doesn't matter how long it lasts. Momentum does not give that team a better chance to win the that game, the next game, or the next series.
Anyway, we seem to be going around in circles with this. You don't want to believe me when I say I'm a strong believer in something, that's okay. But I'm not going to continue debating with you about it.