I don't think there's a limit, actually... I'm logged in on three. A few things to think about:
Any work either of you do will be saved to the one account (depending on your output it might get a bit confusing).
With regard to syncing, you might want to check in occasionally that all work is effectively backing up to Creative Cloud by logging in to Adobe Creative Cloud (My Assets - Mobile Creations).
Does that help?
This sounds like the answer I was hoping for, I wasn't sure if too many people are worrying about mobile app limits in the same way as they might be about desktop apps - Ill see how it all pans out. Thankfully we don't do too much collaboration work so could create folders and keep our files separate.
Thank you for your answer, have a great weekend!
Sure thing Nick.
You'll see this when you log in to that assets page, but basically work is organized by app, so all of your Draw work ends up in one folder, all of your Sketch work in another, etc... Just naming your projects would work though. And, if it got too confusing/crowded you could just export to the desktop apps and save work there. So there are options.
Have a good weekend.