Minimal example: http://pastebin.com/g3rKm0As (you will also need IncubateMe.qml http://pastebin.com/kq4XRkzV)
Steps to reproduce:

• click inside the main window with random interval (for example 10 fast clicks, little delay, another 5 clicks and so on)
• you will see that "incubatedCount" is not 0 when object incubation ends

Example of last lines of activity in output:
...
qml: onIncubatedCountChanged 37
qml: Object IncubateMe_QMLTYPE_18(0x28db9d40) 181 is now ready!

That means that 37 of 181 items were not created.