Wow, they have very similar stories and are almost exactly the same age. My son turned 5 in August. His onset lasted about 3 months and gradually decreased. He was completely fluent all summer. Since school started he has had a few days here and there where the stutter came back, but wasn't severe. No blocks or tension, just saying "um" a lot at the beginning of sentences. His teacher was aware, but only noticed it one day this entire school year. He goes for months with no issues, which is so confusing. So far we haven't proceeded with speech therapy and are ready to support him later if he needs it. I'll be praying for you both. It is hard to watch your child struggle to communicate!