R. Guard: There is no question that "seeking out and reading erotica" is an Isur d'Oraisah. However, depending on the circumstances, it might only qualify as a "slip." I'm concerned with the downside of causing people to reset their hard-earned counts unnecessarily.
On the other hand, in certain cases, this definition of a fall may be too lenient. For example, if the individual finds the erotica accidentally, it won't be considered a fall, even if they spend 3 hours reading it (because they didn't seek it out). Or, a person may spend half the night searching for erotica, but will not have fallen, provided that he doesn't find any (or if he finds it and doesn't read it - an unlikely scenario, to be sure).
You probably don't want to make the rules too complicated, but what about the following?
1.) For someone whose main Nisayon was reading erotica, "seeking out and reading erotica" will be considered a fall, requiring the count to be restarted. When in doubt (e.g. the person stopped after reading something briefly), the individual should explain what happen and await a "Psak" from R. Guard, who may seek input from other members of the forum.
2.) For others, if the reading was for less than 10 minutes, there is a 7-day penalty for the first offense in a 90-day cycle, and a 30-day penalty for the second offense in a 90-day cycle (second offense must be for less than 5 minutes). If the first or second offenses exceed the maximum times, or if there is a 3rd offense in a 90-day cycle (for one minute or more), that would be considered a fall.
Such rules, while more complicated, would recognize that, as harmful as reading erotica is, the damage is not as great as looking at pornographic images or videos, and is easier to reverse.
Hope this helps and that others weigh in.