One thing to keep in mind about IC.  You normally will want to build an IC for 1 of 2 reasons.

1.  Your income exceeds your build capacity.  This is very common for Japan, they have only 1 IC with a build limit of 8.

2.  Your current IC’s are far from battlefield.  Also very common for Japan as they move farther west in Asia.  This also applies to the US & UK to a lesser degree.  Many US/UK players will place an IC in Sinkiang (US) and/or India (UK) in an effort to slow down Japan’s western advance.