That depends.
I have seen addons with 4000+ JS files (unnecessary though IMO).
I have seen addons with JS files that are 20,000+ lines of code.
I have seen addons with many libraries and/or minified/obfuscated code.
These take a long time to review and often have to be reviewed by an admin reviewer.
Addons with attaches sources also are automatically sent to the admin queue.
Then there are poor practices …
I have seen an addon with 3 lines of code which included 2 massive libraries for those 3 lines
I have seen many addons that complicate the code and review, add a lot of function overheads for no good reason.
For example:
var list = "aaa bbb ccc ddd eee".split(' ');
Why not?
var list = ['aaa', 'bbb', 'ccc', 'ddd', 'eee'];
Or …
var text = '';
text.concat('aaa ');
text.concat('bbb ');
text.concat('ccc ');
text.concat('ddd ');
text.concat('eee ');
instead of:
var text = 'aaa bbb ccc ddd eee';
Or …
var list = [];
list.push('aaa');
list.push('bbb');
list.push('ccc');
list.push('ddd');
list.pucs('eee');
instead of:
var list = ['aaa', 'bbb', 'ccc', 'ddd', 'eee'];
Even today I saw 2 addons with 200 lines of entries like above.
So, to answer your question, addons with small amount of code and/or updates with minor changes tends to get done quickly.
After all, one of those large addons takes as much time as reviewing 100 small addons.