So sorry to hear that you're dealing with such severe insomnia. It's very challenging and many of us on this site can relate. I've been taking Ambien for many years myself, but not the extended release. It works best form if I split the 10 mg tablets, taking 1/2-3/4 at bedtime and the other part if I wake up very early (2:00-3:00 am, usually). I can usually get more like 6 hours of sleep that way. Six hours is way better than 4!
I've done Cognitive Behavioral Therapy (CBST) with 2 different sleep psychologists, to try to wean off of Ambien and still get adequate sleep. I wasn't very successful but I did learn some techniques for getting better sleep. I did one program in person and one via tele-sessions on my computer.
In your other post, you mentioned that doctors don't seem to understand severe insomnia. I've had some trouble with that, too, and I find that docs are being told, more and more, not to prescribe Ambien long term. I've had to search for a GP who would prescribe 10mg. Psychiatrists may be more sympathetic because they treat anxiety and depression which are often linked to insomnia.
Wishing you good sleep--