Sunny has done Judo for about 20 years now (since 2000), and washing the Judo Gi is pretty much a daily habit. If done correctly, you will get about 3-5years (Double Weave Judo Gi) and about 2 years (Single Weave Judo Gi) of wear.
Do not tumble dry the gis, let it dry hanging outside. White gi's always shrink more than the blue, so unless you know what you're doing, plan your drying times with your training sessions
It is often recommended to cold wash the Judo Gi for the first wash. Generally, a hot wash would cause the Judo Gi to shrink slightly more than a cold wash. If you know what lengths the arm needs to be at, and the jacket could use a little bit more shrinkage, use the hot wash option if necessary
Set the spin cycle to 400-600. Setting the spin cycle too high might damage the Judo uniform. 400-600 seems to be at a happy medium.
Do not overload the washing machine with clothes or detergent.
I always try to aim for the washing machine to be about 3/4 full. My washing machine is a front loader that holds about a 7kg worth of washing.
Do not mix a white Judo gi with coloured clothing if you're not sure if the clothing will bleed, we too have learnt that the hard way