GOOD TOPIC!
I am a Delphi developer. I am familiar with other languages too (C, PHP), but since I started to use AHK one year ago I am far more productive.
My script consist of two main scriptfile, each are about 300 lines.
CommonHotkeys.ahk - This includes the window-group defines and the #IfWinActive directives
MyScript.ahk - This is the main script that includes CommonHotkeys.ahk.
I use different MyScript.ahk at home and at work.
This is because I have a hungarian keyboard at home and an english at work. The desktop design and arrangement is also different.
Only the CommonHotkeys.ahk is the same.
The main difference is the behaviour of the Middle mousebutton.
I cannot use it inside an #IfWinActive directive because it depends on the cursor position.
I also include some smaller helper script libraries:
WinSysMenuAPI.ahk and
AHKHelper.ahk
And I also have a startap script that run on every time I login. But that is separate from the main script, it runs as a different process and quits automatically when it finishes it's job.