When to change light regime?

Hi there! I'm looking to understand when it is proper to switch light regime for the different growing stage. Most of what I read refers to elapsed time and it make sense to me that watching my girls is probably the best way to know when it is convenient to switch them. Plants and environment are different from one garden to another ... so correct me if I'm wrong ...

What are the signs for when to take seedlings, clones, vegs to the following stage?

I'm not interested in time but visual signs. I also understand that the vegging stage is composed of 2 light regimes 24/0 and 18/6, when it is convenient to make the switch if it is at all?

Can a plant be stressed by an excess of light? if so, what are the visual signs?

I started my crop 12 days ago but I don't their age, any comment?

Thanks, it is almost 420!

YOU can go into flower any time you want, even from day 1.

There are a lot of ways to do it and you can't go wrong with any of them. I light them 24/7 in veg. And then go to flower based on size more than anything, but usually at 5 weeks.

What size are you looking for?

lol, that would be great if I only want to fire a bowl. My goal is obviously to max the yield. So I'm looking to allow as much branches as possible ... does the plant gets tired of being in a veg state?