How should I know what OPT_EXPIRE_TEST is and how/why influences the duration of the splash screen?
OPT_EXPIRE_TEST just exists but is documented nowhere
This is not actually correct, see builconf.inc
# make the build show an "expired" notice after N days. To encourage users of test builds to provide feedback
If you grepped the tree as I suggested earlier, you should have found this. I'm not trying to be a jerk, the reality is CHDK is a big, ugly, poorly documented code base. If you want to work on CHDK effectively, you are going to need to learn how to find stuff and actually take the time required to do so. That doesn't mean you shouldn't ask questions, just that your effort will be better spent learning *how* to find what you want rather than getting an explanation of every little detail.
In general everything with an OPT_ is a compile time option, so if you see one you will want to include the makefiles in your grep.
You could also search the forum for OPT_EXPIRE_TEST, which would get youhttp://chdk.setepontos.com/index.php?topic=650.msg104732#msg104732http://chdk.setepontos.com/index.php?topic=10610.msg104691#msg104691
The second one gives the commit where it was added and an explanation of why it exists.
You could also have found this by search the svn log, or using svn blame on the file where it appears. These are both helpful tools to understand the history of the code. If you use windows, I highly recommend using tortoise. I also recommend grepwin from the same author.