Questions about Kadian dosage limits

I have chronic back pain that requires pain meds to mask the constant
burning in my lower
back.  The condition is progressive spinal/back degeneration from RA
and OA and an
injury from 1998 in a triple rear ender by big trucks.  h condition
will not be correctable thus
I'll be on strong pain meds 24/7 - 365 for life.  The buzz in the
beginning was nice but it soon
faded away and the morphine doses only masked the pain with no high to
it. I started out using
(all prescription of course) MS Contin and worked my way up to the
maximum strength in a couple of years then went on to Kadian starting
with one 20 mg (I think it was 20) every twelve hours and eventually
progressed as needed up to two 60 mg caps twice a day every 12 hours.
That's a brief on my morphine history and use.

So now I'm taking 240 mgs of Kadian every 24 hours - that mask my back
pain but I know
the need for stronger dosage will develop soon the next strength up
seems to be 100 mg.
I was told by my doctors and pharmacists that Kadian is a time
released capsule that will
last for 24 hours per capsule - not for me it doesn't. That's why I
take the amount I take.

Every time I ask for an increase in dosage and strength my doctor
tells me I need to see a pain management specialist and then gives me
a script for more od them in the next dosage
strength up.

So what I need to know from this NG is what is the maximum dosage I
can take before
I over dose.  I'm 62 with multiple chronic medical problems and want
to live in a pain free
existence for as long as possible as I love life.  I don't want to OD
on morphine sulphate
as in Kadian.  So, as experienced long time users what do you
suggest?  Do I go to the
next strength of Kadian or on to a stronger pain killer like Demerol
or Daladid or what else
???

Thanks for your advise - I'm opened to all good suggestions!