I can usually come up with my decision well before my 30 seconds is up, but the time bank is for those occasions I would like longer.
I feel like the biggest key is evaluating the hand mid-game and in advance. For example, on the Flop I'm already deciding what I might do if specific Turn cards come up or what to do if the opponent takes a certain action. By the time those events come up, I'm already a step or two ahead like in chess game.
The biggest reason to anticipate and make decisions before they come up though is for the simple fact that it makes the decision logical. In the moment, the decision can become emotional. I think I should call, but what if they have it...? If you decided beforehand to Hero call then that was decided before the emotion of the moment kicks in and so I'm ready to call them down when the time comes
This was just an example, but you get the idea. Another large part to the decision process is hand reading ability and this is refined with practice and experience. As the hand is going on I'm already narrowing down the range of likely holdings opponent(s) hold - technically, I'm starting this process even earlier...preflop when they decide to raise or not etc. and even earlier than this in live poker because I can gain a lot of tell-information even before the cards are dealt of things like mannerisms or personality