Yes. The T12/T13/T15 cartridge system is a complete unitized heater and temp sensor hermetically sealed away from the atmosphere inside a stainless steel envelope. This addresses the eternal problem that eventually faces all of the old-fashioned slug-in-a-metal-tube type irons; slow response caused by oxidation between the tip and the heater, and inaccuracy caused by oxidation between the tip and the thermocouple/PTC temp sensor.
My MLiNK S4 is an awesome station that highlights this to the extreme; when the handle and tip are fresh and new it solders like a dream. It uses a high-frequency (switch-mode) power supply and a handle based on the now-defunct T-200 soldering head technology that can deliver 90W actual to the tip, plus has sleep mode and a crisp backlit LCD display with set and actual temps all inside a nice extruded AL case with metal face and back.
Tip and heating element are modular plug-in, which is convenient. But as the tip and the temp sensor age and get crusty response time gets worse, overshoot gets worse, everything runs too hot or too cold until you replace the tip and scrub the temp sensor clean with steel wool. Eventually the sensor gets to a point where it crusts up in a matter of hours and you just have to replace the whole handle; the heater is modular but the temp sensor is not.
I wouldn't wait on ordering the Ayima FX-9501 handle; it's on sale right now, and you'll want a spare handle even if your deal falls through and you order a different kit that comes with the right handle. The hack 907/937 handle that comes with is hazard to the controller; if the contacts jam and bend inward, which they eventually always do, they can short out the main power to the heating element. I was just lucky with mine.
mnem
Lessons learned the hard way...
Your point about the oxidisation was well proven today while attempting some modifications to my Heathkit V-7AU I thought to myself that my iron was not responding much to the heat I was putting into it, I had to turn the heat upto 420 to complete a joint that was simple to do. After letting it cool down, I took the tip off and you was right, the slug in the tip was loose and oxidised, so I took a new tip and fitted it and I was now able to solder the same joint at 300 on the display, and the old tip showed no signs of degradation on the outside.
With that, I'm now looking forward to getting my new T12 setup even more and waving that drop in performance goodbye.
Now I know that my Hakko 936D is a clone but I really can't see that a genuine Hakko 936D would have performed much differently given the conditions of the tip which was a genuine Hakko one anyway.
It makes me shudder now thinking back to how I used to use mains heated irons made by famous brands like Salon and Weller before, and even fitting new tips to them, never restored their performance they had when they were new. That makes the sound of the hermetically sealed T12 tips with their integrated heaters even more enticing. Looks like the thread about soldering stations taught me a lesson and did me a favour, so who says that you can't teach an old dog new tricks?