Question

1. It's been such a long time since we've seen each other.

2. It's been such a long time since we saw each other.

(Which one is correct?)

3. It's been a long time since we last saw each other.

4. It's been a long time since we saw each other last.

(Which one is correct?)

Answer 1

All are correct, but I prefer #2 and #4.