He rarely initiates any messages for the last 8 months but everytime when I initiate, he texts non-stop for 3-4 hours and won't let me sleep? Why?

He is a close friend of mine. Any clues? Thanks for helping.
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Everytime once I I intiate, he will lead the conversation and it becomes him talking 60% and me talking 40% and he won't let me sleep till about 3am everytime. Isn't it weird?
He rarely initiates any messages for the last 8 months but everytime when I initiate, he texts non-stop for 3-4 hours and won't let me sleep? Why?
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