I had a rather arms length involvement with that airplane way back in the mid 80's when TAG owned it. They wanted out of it so we tried to sell it to the USAF for a parts donor for their KC135 JT3D engine upgrade program. As it turned out the fact the engines on this airplane had been upgraded from their original non fan configuration as opposed to simply hanging new JT3D's on the airplane made it ineligible for the program. TAG was willing to let the airplane go dirt cheap at the time. It had a very nice interior and was a well kept 707! You would have think that parts would be getting scarce. I'm sure it remains on so sort of low utilization maint. plan and those typically call for parts overhaul or replacement based on the calendar rather than time / cycles so the clock is certainly ticking....