My thought is helicoils are a one time use repair, the helicoil doesn’t always match the length of the threads of your part but will hold torque but any removal or restart of your bolt or in this case spark plug your are taking a chance, I use 10 to 15 helicoils daily for repairs in steel and aluminum and the aluminum is already a hit and miss for the higher torque applications.
I also use solid inserts that we install and use Red Thread Locker and let set for 24 hours for the bigger much higher torque applications (75 ft lbs and higher ) but never any thread locker on a helicol.