Hi Irisheyes,
Well, my arachnoid cyst was discovered in mid '96. I was 30yo at the time (I am now 42yo.). I had surgery a few months later, and had fenestration of the cyst. For me, removing most of the cyst worked, and it hasn't reoccured since. Many people need shunts, but it seems I didn't need one at the time. I've had other associated problems like occipital neuralgia (nerve pain) from the surgery, and balance problems from having Dandy-Walker Syndrome Variant. But things have been mostly good since the cyst surgery, and I'm so glad I haven't had to have more surgery since.
But it all depends on whether the person gets the right treatment from a good specialist at the right time. Often doctors/neurologists/neurosurgeons don't take symptoms of arachnoid cysts seriously. Luckily I found a great Neurosurgeon the first time who was willing to operate...and all went well with the surgery!

~Jaime~