Well just to front load this before you get bombarded by information: The answer here is it depends.
The answer to your "It depends" revolves around what you would like to do with these trees in the future. Growing bonsai from seed is a truely long haul project which requires a lot of foresight into where you want it to end up. Otherwise you'd just be growing a tree at a slower rate then a trades nursery can do.
First and foremost question to be answered is where are you and what is your Growing set-up like. If you are just heading into winter and you don't have a growlight to supply the trees with, then you are truely best off just leaving them as is.
Secondly, you should take some time to analyze your goals. They don't have to be concrete, but aligning yourself on a set of tracks minimalizes wasted effort in case you change your mind on how to go about your journey.
In general, there are two schools of thought on growing bonsai from seed. Slow or fast.
Slowly growing the tree is more or less just clip and grow. This gives you almost complete control over your eventually design with minimal scaring at the cost of many...let's say decades...to get to the final result. Pursuing this process would mean that you should keep your seedlings as they are until they are strong enough for their first root pruning. You can also pursue seedling cutting techniques if you so desire.
Growing these seedlings fast means attempting to do any work on these at the most opportune moment so as not to slow the tree down. With this process, you grow the tree as hard and as fast as possible to get to your "end goal" in a much shorter time frame with potential scars or chop wounds. You also risk loosing control over the growth sometimes depending on the species and your own time devotion. The goal of to control the growth, but let it run until you are satisfied with it.
In general, you also wouldn't want to repot these seedlings when going for the fast method. The idea here would be to plan on how you want to tackle the roots. If you want to do root pruning, then you'd probably be looking at repoting next spring to get the roots sorted. Using the washer/tile method, you'd want to keep the root ball intact as much as possible (to minimize damaging the roots) and slip potting it into its first year growing container. You wouldn't worry about the roots since the plan is to completey remove and regrow the roots at a later date while using the seedlings youthful energy to make it as strong as possible. The next method is seedling cuttings. You'll only want to do this if the conditions are optimal to grow. Essentially, if you plan on going this route then your first opportunity will be coming up very shortly. Take a look at
@cmeg1 threads as he has posted how he went about doing this as well as timing.
I would say, the biggest reason to repot these seedlings soon would only revolve around a matter if health. I'd personally keeps these in their containers until you see the rootball beginning to start circling. No reason to harm the seedlings unless you need to.
Anyways..I wrote this as I was falling asleep so I apologize for anyway weirdness in the sentence structure. I'll be sowing a couple hundred seeds myself in the coming days.
