Thanks! I only have Swift in a Kelly Pochette, so was wondering/worried about the degree of slouching to expect in a B30. Of course I’ve read through the threads

It seems to vary from puddling leather and bulges in the leather from stretching in the worst cases to some bags maintaining structure very well.
Perhaps only using a lighter load inside and usinf a bag organizer from the beginning will be the trick.
Not to distrust anything that SAs say but I don't think Swift it not thinner or thicker now, H craftspeople select a piece of leather according to the item they will make.
I have a 10 years old Travel Web is 45cm and I also have a almost 4 yo Swift Plume 32, both look new. No scuffed corners, no bulges.
Both are made from thick leather (2008 and 2014). I tried a Medor Clutch in Swift before Christmas and the Swift used was
naturally thinner, but then no way could someone roll-up a Medor clutch made from Swift of the same thickness as the leather used for either the Web or Plume, of course it has to be finer. That's not a reflection of quality but fit for purpose. If someone is commenting in thin/thick leathers from clutches and SLGs to big bags of course there are differences, just as there would be with any types of leather.
I've only bought the Web recently so don't know how often it's been used in its past but it's a travel bag and since I've had it it's done
thousands of miles and been used for work. It's been raining, snowing, freezing...There is no time and no way to baby a large bag for work and/or travel. The way the leather works on this bag is a bit like thick Clemence, it undulates like a wobble board but doesn't puddle as in a relax.
The Plume holds it shape due to the way the model is constructed, I see Box versions looking for more more saggy. Perhaps that's because Box leather from some eras tends to be thinner or is more shiny or the bags are so much older or whatever. I store my bag, in a dustbag, stuffed but upright with the handles upwards to stop 'smile' marks (B handles will stay upright anyway). I'd prefer to store the Plume on its side but then I'd need to keep it in its box and with me that means not so handy so I wouldn't use it as often. The next time I carry it I'll take a pic.
Swift leather undulates like Clemence but can hold it's shape depending on the model. I'm sure a Birkin would be made with wonderful thick leather, but the whole nature of a B is a casual tote. A 30 will stay looking more structured than a 35 but the B (a cut down version of an HAC) was designed to look casual. With Swift you should have a fine and smart look with the relaxed B style, best combo.