instance, instants, stance

Instants or instants is the plural ( more than one ) of"instant", meaning a second, a minute, or a very brief span of time--
It was all over in a matter of instants.
We can have this ready in an instant, or possibly two instants.

Instance or instance ( rhymes, or nearly rhymes, with instants )  means case, example, or occurrence--
Make sure you include the pertinent facts in your report--for instance, the date, time, and location.
He has been suspended several times, and each instance was more serious than the one before.

Stance or stance means position or attitude--
His stance on gun control is popular with the voters.
His tough-guy stance made the police officer suspicious.

Now that you know that, you can say--
"His stance on discipline may change in a matter of instants if there's another instance of the same bad behavior."

Note--"instant" may also mean precooked or premixed--
This is instant coffee; just add hot water.
"Instant" may also describe something that happens in a brief span of time--
The internet made him an instant celebrity.
"Instant" is also an old-fashioned way of saying in the present month--
I received your letter of the 10th instant...
Note # 2--"instances" is the plural ( more than one ) of "instance", meaning case or occurrence--
It's best to follow the standard procedure in all such instances.