I was on 1200 of XR for years and up to 1500 mg in the final months while we tried to get it to work just a little longer.

One trick that worked for me for years with the XR was that I took nearly all of my dose as XR and broke one tablet which made it instant release. That helped me fall asleep but then I was so knocked out in the morning compared to taking 800 mg of IR at once (I couldn't have done this; 600 was the max I could take of IR and work. I begged to go on ER as soon as it was released).

It made a difference for sure; a couple times when I was IP they didn't have XR and I was given IR. I'd go in complaining of not being able to sleep for weeks or months and then they'd give me 800-1200 IR and I was out like a light for a few nights until my body adjusted again.