Does Helix work best for noobs?

Does Helix work best for noobs?

Not necessarily, please see the thread -> : The Best Aneros model is....

Context here is that I'm a very well-practiced gay bottom, and I have experienced virtually no involuntary contractions after months of using a Helix.

My intuition tells me you may so used to the macro sensations from stimulation due to penile/dildo stimulation that you may be dismissing the more subtle, gentler sensations being generated by your Helix. This is a mental challenge more than a physical one. Employing your well developed patience to fine tune your mental focus may pay dividends here.

I also see a lot of information about holding mid-strength voluntary contractions in sphincters and PC until fatigue. How many hours of that is required to reach fatigue?

For me it is certainly not hours, while I have developed the ability over my years of experience to hold a contraction for longer periods of time, I've also developed a sensitivity to recognize and encourage those involuntary contractions to occur more quickly than when I first began my practice. This is somewhat of a conumdrum to explain, just another paradox in the Aneros journey.

So I'm starting to wonder if I've already trained myself to control the reflexes that make these work as intended? Or are there ways to take advantage of having strong control?

As I mentioned above your primary mental focus may be on recalling the macro sensations generated during your bottoming experience. By refining your mental focus toward the more subtle sensations created by your Helix I suspect you will enhance your pleasure response. Here's my advice, take advantage of your muscular control abilities by employing your PC, BC, rectal and sphincter muscle groups in various combinations to produce varying movements/sensations. Try holding only one set of those muscles constant until fatigue sets in and the involuntaries start to occur. Try to remember the sensations at the onset of these subtle involuntaries so you can focus on recreating them in future Anerosessions. This type of practice will build up subconscious muscle memory making transition into the orgasmic zone easier.
Good Vibes to You !