How long till the next top on the first set of two tops
As long as the plant has the ability to recover, and has enough growth for a cut, you can top. It really depends on your goals.
I wouldn’t top an Auto more than a couple of times, but a photo-sensitive plant can potentially be topped and unlimited number of times.
As i do not use Autos, I personally top every node, continuously, until a couple of weeks before flower. This method slows Veg growth severely, but makes for a very bushy plant. In my case, it works very well.
You may also want to look into low stress training (LST), or super cropping, for different results.
Hell yeah mainlining is awesome… The plant just looks so clean and if you lst along with mainlining the plant has the potential to be huge!! Check out my grow strawberry kush and white widow… The one in the back is mainlined into my scrog screen…
I have some autos going and topped once and it did slow her down a bit compared to the other 2 the top colas are bigger on the one I left alone