last time vs the last time, next time vs the next time. When should one use the definite article?

Question

I've been noticing the following phrases and am puzzled by the inconsistency in using the definite article in them. How does one know where to use the definite article and where not to use it? What is considered formal and what is not?

Next time vs the next time

• Pinkman: "The next time, put an ice pack on your head during chemo."
• The next time you’re in Ireland, you must come and visit us.
• He will pay for food next time.
• Next time you see him, tell him the truth.
• Maybe next time.
• Next time when our band rehearses, I'll be playing the drums.

Last time vs the last time

• What about last time?

• Last time I saw you, you looked upset.

• The last time I saw him was at his wedding.

• He sprouted a beard since the last time I saw him.

• I paid last time so it's your turn.

• Last time I went to the dentist I had to have two teeth out.

• Where did we leave off last time?

Answer 1

Well, according to this teacher (https://www.youtube.com/watch?v=sX68G8EAczA&t=667s) the answer is: I can use either option.

Next time and the next time as well as last time and the last time time are interchangeable in all given contexts, that is if the last time and last time mean the previous time and the next time and next time mean the following time.

The versions of the sentences where the definite articles are ommited are considered informal and used in everyday speech.

When the meaning of the last time is the final time the definite article is mandatory.