When to use pretrained word embeddings?

[hipoglucido]

Hello, I was wondering when do you think is worth to use a pretrained word embeddings model. I am facing a one-to-many problem as well, where my "many" are text paragraphs (~80 words). I have 100K training instances. What do you think?

Also, if I were about to use a pretrained word embedding model, where should I insert it in your code?

Thanks in advance.