I have a factory installed 2000 lb system in my TR-182. I use it with
cannulas equipped with a flow meter. With this set up I generally get
about 20-30 hours from an O2 fillup. I use O2 from about 11K up, 8 K
at night. Above FL180 I have to switch to a mask, as per the FARs, so
I generally don't bother going up there.

Michael