Over the decades, I have met hundreds of Christians who went into full-time Christian work, and then didn't last for more than a few years. Most of them went four years to Bible college. Here in Mexico, we have had several that came to work full-time at the orphanage and then left within a few months. And when I was in college, I realized that there weren't enough churches to hire all the students who were studying for the ministry. Five missionary families, who had raised support, arrived here after I did and have quit and left.
When I taught Christian school, I quickly saw that less than half of all Christian school teachers enter their third year of teaching, despite four years of college. (For the record, I taught Christian school for ten years). Churches quickly fired teachers, sometimes unjustly, because there was always a steady supply of newcomers.
I also observed that Christians who held secular jobs, and who could afford to leave a church and go elsewhere, got treated better than the people in full-time service. From those people, not from the Bible college graduates, long-term church leadership emerged.
Your whole duty to God is to Fear Him and keep His commandments. Going off to Bible college or into a full-time ministry takes a very special call, and almost all who accept that call do not succeed. Most Christians need to go to a good church and serve God from there.