ABA form is like a musical sandwich. You have the 2 slices of bread with the contrasting meat and cheese on the inside. Instead of bread and meat, you use musical materials. Perhaps an 8-bar phrase for the A section followed by a 4 or 8-bar phrase for the B section. A nice little musical sandwich.

A piece of music made from ABA form can last anywhere from 45 seconds to 5-6 minutes or longer DEPENDING ON HOW THE COMPOSER UTILIZES THE TOOLS OF REPETITION AND CONTRAST!

For example, I can take an 8-bar phrase, repeat that twice, play another 8 bars for the B section, then back to the A section again for another repeat (with variations of course). Now, how long will that last? It depends on tempo or how fast the piece moves through time. Most small ABA sections don't last longer than 2-3 minutes. Why? Because if they were repeated for longer periods of time, the music would become dull and repetitious.

BUT, if we create another section of music - the C section, it provides the relief the ear is searching for and we can then repeat the entire thing again so the form would look like this: ABACABA. This form extends ABA and provides the necessary contrast to create longer pieces.