I have successfully help my BB to change to 2號奶粉 now. I have used 3 weeks-4 weeks to change.
At first, I add one meal of #2 every 3 days for 3 cycle, then 2 days for 3 cycle, then 1 day one meal for 3 cycle, and now I have no #1 milk at home. (of course you have to make sure that your BB have poo poo each/every two day)
When my baby was 8 months, I have used 1 week to change to No.2 as per the recommended schedule of Wyeth. (i.e. try No.2 once the first 2 days, twice the second 2 days, three times the third 2 days). His poo poo is better as compared when he took No.1.