How can one tell when they are reading the scriptures enough? They tell us that we are to feast from them, and not nibble or snack. So how much is “enough?” How does one tell when they are “full” from this kind of nourishment?
I can’t really answer this question for you because the answer for each person may be different. This truly is a “times and seasons” of our lives sort of thing. For example, an older retired gentleman will likely find that he has a lot more time to dedicate to scripture study than he did when he was younger and struggling to support a family. A full-time missionary studies for two hours a day, one hour of personal study, and another hour of companion study. But then they go out and talk to investigators and members about the gospel all day, so in that sense the number of hours they spend are innumerable.
To answer your question more directly though, this is a question you need to prayerfully consider for yourself. A couple of things to consider:
Are you enjoying reading the scriptures? Are you excited to pick them up, wondering what you will learn today? If the answer is no, then likely something is missing in your scripture study. Perhaps, more time, more prayer or more effort is needed.
If you, after your study of the scriptures feel happy, enlightened, and most importantly you feel closer to God and have a desire to serve Him, then you are likely studying them enough.
In short, is your time spent studying the scriptures making you feel closer to Him? If not, then work harder. If so, then continue in that good course. The main purpose and design of the scriptures is to bring us to Christ. That is the key.