My "workhorse" wetsuit that I bought 6 years ago (custom, $250 Cdn) is still going strong because I turn it inside out & rinse it in fresh water as soon as I can. It's a bit faded, and I've torn some holes in it by...er... sitting in the wrong place at the wrong time
But it's still in good condition. Good enough that I still wear it quite a bit.
For washing, I tend to use anything from the supermarket that is market as "gentle" or "for delicates"; stuff like Woolight, Zero, etc. IOW, nothing caustic.
Again, after turning it inside out I semi-zip it so that it will hold some towels inside. When wet, these keep the suit underwater in the machine. I also pile other, larger towels on top of the suit so their weight will help keep it underwater while in the wash cycle.
I use only cold water, on the "gentle" cycle. After it's finished I unzip the suit, take out the towels, and hang it to dry (still inside out) on a big plastic hanger that has no sharp edges.
The suit has not lost it's shape, and everything seems to be still working after 6 years, so I guess I must be doing something right.
BTW, rinsing ALL your gear in fresh water after use is a good idea.
~SubMariner~