Once again:
There are certified, published operational limits. As long as ALL these limits are observed, the engine should run fine at MCT until fuel is exhausted. Is oil temperature not one of these limits?
A bit more background: For almost a decade, I carted a hi-bypass fan around the world, with a portable instrumentation data package, conducting cell correlation tests at airline facilities. The engine had some tired and obsolete hardware, and so was not airworthy; but for comparative performance purposes, it was stable and an ideal transfer standard.
I ran the engine per a test plan THAT IGNORED ALL T/O TIME LIMITS.
EGT, speed, oil pressure/temp. etc. limits were observed, but OFTEN I spent 30 minutes or so, continuously above MCT, at various T/O ratings. THERE WAS NEVER A SAFETY ISSUE with this operation schedule. The only failures my team incurred were when some customer-supplied equipment broke.
If a Trent would be at risk in this sort of operation, I have to question the design standards employed.
(Footnote: Oh, yes, one time when "my" engine was being ground-shipped, the lorry driver took a shortcut - and bashed the engine into a rr overpass!
)