Hello!
This is just an experiment, but it works as it should, no matter what you do, you will not be able to store any properties, unless you explicitly write the properties to disk, and reads them back in.
The approach in the code, is also proven to execute less appleevents, as the the events will be routed from the applet to the StandardAdditions.osax which from then onwards will send and retrieve apple events with any applications targeted.
All in all a pleasant model for making applets! 
I have added a handler for opening stuff as well, to show that it works for droplets as well. This is meant for a run and die applet, but I think it should be equally easily to adapt the concept for a stay open applet, with a runhandler, just returning the idletime. which is then returned by the on idle handler in the applet.
The construct would be something like this:
on idle
return run script idleScript with parameters {theStuff's whatever}
end idle
The idleScript would then also have theStuff as its parent, in order to share data during run-time, which will evaporate when the applet quits.
I challenge you to try to make the applet quit, and display a value of a higher than 0 when showing the dialog!
(Retaining the script construct within of course!)
-- property parent : AppleScript
property toplevel : me
property a : missing value
script theStuff
-- property parent : AppleScript -- not necessary
-- property a : missing value
to reader()
--global a
tell me
activate
display dialog "this is A : " & a
end tell
end reader
to writer()
-- global a
try
set a to a + 1
on error
set a to 0
end try
end writer
end script
script babyStuff
property parent : theStuff
on run
writer()
reader()
tell toplevel to quit
end run
end script
script biggerStuff
property parent : theStuff
on run {what}
writer()
reader()
tell me
activate
display dialog ("ouch! you dropped " & item 1 of what as text) & " on me! a is : " & a
end tell
tell toplevel to quit
end run
end script
on run
-- global a -- wherever you want, it won't get saved.
run script babyStuff
end run
on open theItems
run script biggerStuff with parameters {theItems}
end open
on quit
continue quit
end quit