I’ve been reading many posts on here and other forums about removing duplicate strokes in illustrator, so that paths are not cut twice. I decided to do a little rooting around in Illustrator to find out how to do this - as I wondered myself.
Turns out it is quite easy, so I made a mini tutorial. I hope it’s useful. 
That is a lot easier than what I had figured out!
The only issue I saw was that it generated little extra dots if your lines join in the middle. In the original drawing before outlining this was a 90 degree angle.
It was easy to hunt those down and delete them though.
I think the problem is that you are not snapping the lines together accurately enough. I would use ‘snap to grid’, with the grid set at 50% of the material width. Then you shouldn’t get those overlaps.
Learn something new every day. Thanks for teaching me this!
Another very useful Illustrator command is Select>Object>Stray Points and delete them all.
This will select all the points that aren’t connected to another point. It saves a lot of cutting time. The laser will see the stray points and go to cut them and just burn a little dot into your project.
I did use the snaps, but it happens when you have lines that end on other lines, you have endcaps on (the little roundy bit at the end of the line), and you run outline more than once. You just have to remember to select all the paths and turn off the endcaps if you need to rerun the outline command.
