I'm about to answer my own question about the durability of the fix.
Today, my bike unexpectedly didn't start at the touch of the button. Instead, it made a series of sounds and noises described in the first post.
I'm sure the spring broke.
I'm debating whether to get a whole sprague clutch or do the cheap fix again.
Right now, I'm into doing the cheap fix as I'm not planning on taking the bike far away from where I live anytime soon. If I were to do that, I'd consider replacing the whole unit this time.
On the other hand, the spring from the O-ring seal lasted good 10.000kms with no problems at all.
KTM 640 - The wheelie monster
Husqvarna TE 250 - The little beast
Husqvarna 333R - The ...umm..... how do I put it....