Yeah I completely agree with this.
I think it's good practice for the add-on ID to match the directory structure from the library directory, e.g.
Add-on ID: YourAddOn
Would have its files located in: library/YourAddOn/
As a more practical example of where this is useful, I have been doing a heck of a lot of work for AVForums. To be organised I have been using AVForums_ as a prefix and locating files like this:
Add-on ID: AVForums_YourAddOn
Files located in: library/AVForums/YourAddOn/
Most desired add-on IDs wouldn't exceed the limit, but sometimes they might.
Increasing to 50 should be a good compromise.