I've had insomnia for years too. The first month of vaping, I think my sleep was worse from getting too much nicotine to make the switch. People suggest dropping nic levels a few hours before you sleep, I did try to dilute a juice with PG and didn't find much different. I think it only affects some people's sleep for a few weeks at most and has more to do with having too little or too much nicotine.
I'm sure you're right.... and mine is improving.... I'm still up catting around later than usual, but I haven't seen 4am in many nights now, thank God! Chasing a nearly-two-yr-old is hard work on 3-4 hours sleep! It was zombie-tyger there for a few days lol