1. He died at the age of 70.

Question

2. He died at 70.
3. He died when he was 70 years old.
4. He died when he was 70.
5. He died aged 70.

(Are all grammatical?)

6. You will be taller than her in a couple of years.

6-1. You will be taller than her in two years.
(Are both the same?)

7. The next few years, you are growing in and out.

7-1. The next few years, you will grow in and out.

(Are both the same?)

Answer 1

#'s 1 though 5 are all used and are correct.

Both of the #6 sentences are incorrect. You will be taller than SHE in a couple of years (or in two years)

Neither of the 7 sentences make sense.