Answer, 18 years since September 1986.
My first Unix system was a PDP 11/44 running AT&T Version 7 Unix. Used for witting COBOL using ed and unipad editors. I was particularly good with "ed" which if I remember was also in early versions of MS DOS. You couldn't get me off the system which held about 24 VT100 terminals. Many a late night waiting over vt100 terminal for compilation and waiting at the line printer for that COBOL program to print.
Picture of PDP11-44