The intercooler lowers the temp of the charged air, so you will be more performance more of the time. It's not necessary, but I'm glad I have it.
Some people wait until the warranty has expired, other people have it done prior to delivery! There is no "correct" time to get it from a technical point of view. So it's really up to you.
I had it done at 1500km and that was painful enough for me.... coming from a Polo GTI, lol.