Instance specific timer

I have a bunch of objects, lets say monsters moving on the screen, they are randomly generated every 5 seconds.

I want each monster to drop say an egg every so often

i tried using a system every 3 seconds drop an egg, but it means that each instance of a monster drops an egg at exactly the same time

is there a way to say each instance wait a random amount of time then drop an egg?

I got it sorry, used an instance variable on the sprite, incremented it each second, so in a way it has it's own timer so when it has been on screen for 3 seconds it drops an egg, thanks