Too long.
You could have mentioned the planned life of the USAF equivalent of the VC10. The KC135 may be in service to 2040 although competition momentum may allow its earlier retirement.
"That will require that the youngest KC-135Rs of today will still have to fly missions 30 years from now. They will be nearly 80 years old."
Although there is a programme to replace the VC10 we cannot say that it has any momentum. Also we do not have the economic muscle to hustle sufficient tankers into service.
Your proposal to re-engine would seem a good one it that was the limiting factor.