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Replacement parts for General Electric TPX24BIYFBB Refrigerator | AppliancePartsPros.com

[COLOR="Blue"]With manual defrost timer AP2061695, starting from the "force defrost click position", if I rotate clockwise LESS than the default setting, will that force more frequent or less frequent defrost cycles?[/COLOR]
No. There is no adjustment for defrost frequency or time on the timer.

[COLOR="Blue"]Or, does the amount of rotation affect the duration of the defrost cycle (pending cutoff by the defrost thermostat?)[/COLOR]
No.

The timer is just a motor which rotates a cam. The cam has a switch on it and an indent which controls cool and defrost. In your case it is 35 minutes every 16 hours.
As usual I cannot find any tech info on this unit, GE likes to keep things a secret. I cannot tell if the timer is constant or cumulative. In constant the timer motor runs all the time, it is wired directly across the power input. In cumulative the timer motor only runs when the compressor is on, it is wired in series with the thermostat, so in cumulative the defrost cycle is less frequent.

[COLOR="Blue"]I have a new timer and heaters but ice is still building up over time, though much longer time (weeks instead of days) compared to before replacing those parts.[/COLOR]
I am assuming you have a dual heater defrost (Item 230 in Section 3).
Force a defrost and confirm that both heaters are coming on.
Check the defrost thermostat, it in not uncommon for these to go intermittent. Often you can see that it has swelled out (deformed) in which case it definitely need replacing.
I would also check the freezer temperature. It should be 0 to 5 degrees F.
If higher it could be that the timer is cumulative so the compressor runs less and the defrost is less frequent.

[COLOR="Blue"]I'm thinking that slighly more frequent or longer defrost cycle will fix this?[/COLOR]
It probably would but the only way to do it is to replace the timer, I think.

Hopefully someone else will jump in with more suggestions.