Unless there's something I missed there shouldn't be any limit (new crazy idea: make a photo with an exposure of weeks or months...). I think the first limitation would be software crashes but the Chronos shouldn't have this problem even for multiple days exposures.
But you'll need a very good mount to track what you want with no smearing.
I dont think mounting is that big of an problem. There are some good Star-Tracking Mount you could built on your own and get solid results, even with high-Resolution-DSLR´s. And there are enough commercialy available also. And you could always just mount it on an solid Tripod and dont move it at all for everything else not involving Star- /Sattelite-Tracking.
.
I think you will run into problems with your exposure way bevore you get problems with an (reasonable good) Mounting Solution, if we talk about Deep Sky and Astro-Tracking.
Light pollution of the Sky and all that stuff...
At some point you will just overexpose your image because of ambient light sources.
That is also the Reason why they would take a lot of single exposures (which still could be several minutes or even hours long) and Stack them /interpolate them in Software to get more detail out of it.
.
You COULD expose for whole days or even longer with a camera however, but then you need a lens with a super small Apperture, some realy dense ND-Filter (Or stack some Up), a sensor with super low light sensitivity, or a place to Photograf with almost no light at all.
Thats were you get into Pinhole-Lens-Territory...
People have done stuff like that and did exposures of multiple weeks on an simle sheet of plain white office paper with an pinhole. The Sun in frame and all the light beeing projected all the time trough the lens onto the paper will "Burn" /bleach the image into the Paper and it will remain visible. Look it up if you want to. Also its quite common for Large Format Photography to use Appertures Like f/64, f/128 (and the Film in the Camera is also not very light sensitive...) combined with exposures of many minutes up to hours.
But for the chronos, i think it might even have an sensor too sensitive for such long exposures, if we are talking stuff like Landscape photography.
.
IF you could make it work in terms of getting an properly exposed image (not overexposing) with that kind of exposure-Times per Frame, then it should be able to make even Day or Week-Long exposures

.
I seriously never thought i could get hyped by the idea of using an highspeed-camera for timelapse, astro- /night-Stuff and Pinhole Lenses, but this is just an crazy cool idea.
Now i realy want to see someone push the exposure time to the limit for some Long Exposure stills. Should be an phenomenal Camera for Night timelapse and Hyperlapse then, because of the absolutely free defineable shutterspeed and framerate
