I started studying Spanish in high school. When I read novels in Spanish, even after 15 years of studying the language, there are still words on every single page I don't know! Imagine what it is like for your ESL students who have been in the country for 5 years and "exited" from ESL.
I took three years of high Spanish. I attended an immersion summer camp, and had intensive one-on-one tutoring in Guatemala for 5 weeks after high school. I continued to study Spanish in college and studied abroad in Ecuador for a full year. Then, after college, I taught in a bilingual classroom for 5 years. You could say that I am fluent in Spanish. I've passed the Praxis exams, taught full-time in Spanish and passed all of the required interviews to do that in multiple districts. I do not say this to brag, but to point out that I have been given many more opportunities than your average ESL student.
I still have a vocabulary gap. Even after 15 years of studying, there are thousands of words I do not know. I am reading a great book, El Idioma Es Musica, in Spanish right now. I fully understand what I am reading, and yet on every single page there are words I do not know. Every single page has at least one word.
When I stop and think about this, I remember that all of our ESL students need help with developing their vocabulary. Even after they are no longer receiving services, they are going to have gaps in their vocabulary. I must always remember that even though some of my students have exited services and talk fluently, with no accent, that they are still second language learners. While all students need vocabulary instruction, our ESL and high-poverty students need extra support in expanding their vocabularies.