Only infrequently in this group do we get to post good news, so here we go.
This is something I never thought I would say, but I have stopped using intermittent catheters. My post-urinary retention has never been severe, but my urologist predicted that it slowly would get worse, given my pelvic nerve trauma and age.
An incontinence technique routinely recommended, but one with which I never have had success, is double voiding to more completely empty the bladder. However, I have been judiciously practicing my Kegel exercises and timed voiding in order to keep what control I have. Over a period of many months I have been surprised that I slowly have been regaining some ability to double-void. When I have been able to do that I have noted that my measured PVRs slowly have been decreased. Gradually I have reached a point where my PVRs after double voiding are so low that my urologist has said that I can stop self-intermittent catheterizing.

This is, of course, dependent on my continued success with keeping my PVRs down, so I periodically will cath to check on that.
My thanks to all gave me excellent advice about intermittent catheterizing and external catheters. You all are appreciated.
--John