I use Olaplex weekly, I probably don't need to use it that often, but I enjoy using it and I love the results so I will continue to use it.
I use:-
No 0
No 3
No 9
and the 4 in 1
I love the serum, I like it both when I air dry and when I heat style. These days I can air dry very easily now and the serum really aids that process.
I really like the oil but I have other oils that I prefer more so I wouldn't rush to repurchase that. I don't use the shampoo and conditioner, and it sounds like I really saved myself some coin there.
The leave in is okay but I find it very heavy for my hair so I won't be repurchasing that.