Nota, since winter is coming, plant growth will slow down..I'd wait until spring, especially if you're considering cutting roots..
One thing you can do is divide in half, but then you'd have two of the same hibs, etc.
I don't consider Hibs plants that go dormant in winter..My hibs bloom yr round so this tells me they don't go through dormancy..In fact, Mr. Crockett from Victory GArdens states this in his house plant book. But, if they're getting little sun, something we can't control, (natural sun) they do slow down..I bought 3 hibs in summer, repotted two. One's in a 10" the other a 12. I'll keep them in these pots a couple yrs..Some of my smaller hibs that are a few yrs old were repotted in spring..I noticed roots growing out of a few pots but decided to wait until next yr to repot.

Are you seeing roots on top of the soil? If so, then I'd say the hibs are really potbound. You mention the soil not drying too fast though, so I'd wait..As long as you're not watering daily because leaves are wilting you shouldn't worry about repotting. Do you have pics of your hibs?

Bays grow big..is yours a tree or bush? They grow into standard trees if bottom branches are kept pruned. The trunk will thicken, too.
The Sambac grows in winter, also, like hibs. Is your jasmine the Maid of Orleans? Sorry, don't know the botancial names for these plants..Toni

Here are some pics, but mind you, all these pics were taken when I just acquired the plants-about 9 months ago.
They're significantly bigger now:

Wow, I need to update my website coz all these pics are so outdated- but just haven't had the time!!

Hib 1
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Hib 2
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Bay
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Obviously, these are plants that cannot be divided, unless yours has multiple stems and crowns that I cannot see. Even so, dividing is a much more traumatic event for plants than a conservative root pruning.

Root pruning is a practice that can be done to all of your plants, but I would wait until the spring of the year. Hold off on fertilizing throughout the winter, and then perform the 'procedure' without fear. Take some from the sides, as well as the bottom. Be sure to replace your plant (in the same container) at the same depth that it was originally. In other words, don't bury the crown and top of the root mass in fresh soil.

Have all of your materials ready and waiting so that your plant doesn't sit out in the air while you get the potting medium ready. After the repotting, water and water your plant to insure good soil/root contact....and then replace back on your nice window sill.

Don't be surprised if you observe a real surge in top growth a couple of weeks after the root pruning. It's a real boost.

Yeah they can't be divided. My sambac (didn't show a pic of that), which has really grown out of control, can, though. Maybe I can try dividing that once the current flush of flowering is through. I'm thinking of doing something with it this w/end. They're basically several individual cuttings in a pot, so it won't be like dividing from one singular plant- so maybe it won't be soo traumatic. It's become quite root bound though so I definitely want to try doing something about it now.

Wow- I'm going to have soo many little sambac starters after I'm done. I've got several rooting at the moment.

As for the ones with pics above- I guess I'll hold off till spring- unless they start showing signs of being in stress from over crowded roots.
Btw, I apologize for those pics above- I didn't mean to show off or anything- I just tend to take pictures only when a plant is showing off pretty flowers- so that's all I have.

We LOVE pictures of lovely plants!

Nota, don't apologize. Its always nice to see pictures of blooming plants. Especially this time of year here in NY. I love the fall mums and colors, but that hibiscus looks so fresh and perky. More like spring! Sandy

Hah- that pic was indeed taken in spring- it doesn't look as perky right now but it just bloomed one of those pretty yellow flowers this morning. Actually it's been by that window (but now it's in a bigger pot) all year but the weather suddenly got a lot colder lately and a lot of leaves turned yellow. Ughh. My other two hibs don't seem as sensitive to the weather change. This one grows more voraciously though so I'm not too worried.

Nota, I love your plants..especially that double yellow hib..There's something about yellow hibs I'm attracted to. Are you going to repot the hibs? They'll slow down in growth but if light is good, will send out flowers all winter..how pretty..Toni

I'm going to go with the "if it 'aint broke, then don't fix it" thinking. So no, I will not repot the hibs now. They seem content and growing leaves aplenty. I will just repot my sambac this weekend- that definitely needs something done- maybe I'll just untangle the roots, trim them a bit and put them back in the same pot- but I can tell it's quite congested down there. I can barely poke a finger into the soil.

I will try and wait out the winter before repotting the hibs. I'm just really impatient!!

Oh, maybe you can help with something else though- one of three hibs (not shown in the pics up there) hasn't yet flowered for me. It tried to send out quite a few buds starting late Aug but then it suddenly got cooler in Sept and most yellowed off or remained stunted. I haven't really had a problem with the other two hibs with yellowing buds. A couple here and there if I move them around too much but if I don't touch them, the buds will flower. This third one seems to be real picky. I believe it will have peach flowers once it does decide to give me a gift.

This particular hybrid also grows much slower than the other two. Is it just a fussy hybrid and that's the way it's gonna be? I fed it (but no, I still haven't gotten around to buying hib food- I know I really need to)regular miracle-gro during the summer.