When I had more time to practice in an earlier phase of my life, I ALWAYS dedicated time daily for working the technique and mastering of 5-finger exercises, scales, chords, arpeggios, octaves, etc. Now, I have no time for that and am trying to survive in the desert with only the shirt on my back; it is a much less successful proposition this way, but it is all that I can muster.
I'm curious (since you seem to be technically much more advanced than me): Do you mean that your overall technique became worse since you have stopped doing technical exercises regularly?
Considering myself, my impression is more that you cannot really loose technical abilities that you have once acquired. Of course under the assumption that you practise regularly. So my experience is that you can keep your current technique quite easily, but of course have to work hard to acquire new skills.
I would answer you that it is in almost everyway like an athlete or dancer that has been away from it. My endurance, finger independence and accuracy (in scales, chords and octaves, as well as trained
-relaxation) is not what it used to be. There is a lot of marksmanship and muscle memory that needs more than just a reawakening. Strength is OK now, but even that was decreased when I restarted months ago. However, you are correct in that my essential
technique is still mine (the way
I hold my hand and move my fingers, the way
I play scales, chords, arpeggios, octaves, etc. is still the same [I agree that once acquired after hard work, I don't think that changes]). It would be interesting to me to consider if instead of delving in to repertoire starting 10 months ago, what if instead I had just dedicated this time to regaining technical abilities for 1 year instead, and THEN went to the repertoire. That may have been the smarter thing to do, but I gave in to the temptation.
I'm sure my situation is not unique for the members of this forum, with so many coming back to their first love after a hiatus, as I too am doing.