Bumping this message because I've seen the same slow loading IDML in CC 2017.
Has anyone else encountered this? Any ideas why the IDML would load quickly in CS6 and CC2014 but slowly in the two most recent versions? Are they any InDesign settings I should look at in particular?
Likewise, ours are taking between 5 and 10 seconds and they are mostly super simple single page documents. Even our InDesignServer instance (also CC) struggles with them. However it loads INDD's in a fraction of the time.
You should only load an IDML file once. Then you should save it as an INDD file.
Here's the reason it's so slow: IDML is not in the InDesign file format. It's an XML file which describes the structure of what's in an InDesign file. It has to create a new INDD file every time you open it. It also has to build a preview for each of your placed images because that's not stored in the IDML.
As I said in my original post, the IDML file wasn't slow to load in CS6 or CC2014. In those apps, it would open within a second or two. In CC2015 and 2017, it takes at least 10 seconds to open.
What's changed in the more recent apps to cause IDML to open so much slower than before?
Why would you need to repeatedly load an IDML? Save it as an INDD file.
IDML files are used as a temporary way of clearing corruption from a file, or back-saving for another user with an earlier version of INDD so they can open it up.
It's not intended for the way you're using it!