your current milk cannot be used for 6 months +?

If can, I suggest you continue until your kid is out of the milk's age range.

Cause you change milk there is always a risk she constipated/sotmach upset etc.

For my kid she started with ENFA, and continued with ENFA Stage 1 2 3 4 etc. I always stayed at the lower stage until her age is out of the range.