Answering the sorta-hijack since the whole thread’s topic has already spread a bunch …
Things run not so much “close to failure point”, but rather “as close as we can engineer them to last the specified lifetime under the stress they face. Which lifetime is multiple years, not minutes.”
The nature of both RPM and of heat stress is that the consequences of exceeding the safe limits are non-linear. The stress on a rotating part goes up at the square of the RPM. A part that will live happily for years at 1500C may begin to soften at 1700C and may fail catastrophically at 1800C. So running at redline may be fine for years, while the lifespan at redline+10% may be minutes or seconds. Naturally the “redlines” are set back a little to allow for calibration errors, tolerance stacking, degradation over the parts’ lifetimes, etc. And true redline power is actually only rarely used; most of the time we’re backed off 5 to 10 to 30% both for needs of the mission and for improved engine longevity.
So an image of a cartoon machine shaking on its foundation with little bursts of steam coming from rattling random pipe joints is inappropriate. Instead think of a machine producing prodigious amounts of power while humming along nicely at a pace it can sustain for years. But doing so only by dint of great expense in the science and engineering behind it, the materials used, the precision of manufacturing, diligent care in operation, the thoroughness of real-time health monitoring, and the (occasional) quality of maintenance.
For darn sure if you removed the fire and added an electric motor, what’s left hardly deserves to be called a “jet engine” or a “turbofan”. A lot of failure modes, and expense do get left out. You’re 100% right about that.
The remaining parts in common, namely the fan and shaft, won’t necessarily be much changed. Then again, like everything in aerospace, they’re already designed to that same sharp edge of maximum performance per weight, size, and durability.
You’re not going to be able to, e.g., bump the fan RPM by 10% without redesign. Because if you could bump the RPM by 10% without redesign, that meant either a) you could have run the conventional with-fire engine that 10% faster, or b) you goofed and overbuilt the fan with 10% more durable capacity than you were using in the with-fire engine.
Now when you remove the fire and add an electric motor you also add in all the failure modes of the motor itself and whatever other new gizmos power and control the motor. All those things are fairly new, at least new to aerospace. So all those failures need the be designed for and around. And mitigations put in place.
Monster electric motors are not new. But the engineers are trying to take locomotive- or ship- scaled motors and make them (comparatively) small and light. That means extreme power densities. Which brings heat rejection issues and another dozen challenges I personally know nothing about.
Once the kinks are worked out there’s every reason to expect electric airplane powerplants to be orders of magnitude more reliable. But there will be kinks to work out, despite the best of 21st Century engineering. It’s a fast-moving field right now and the frontier of best practice is moving rapidly.