How often should sparkplugs be changed in a ETEC?

[dodgeman9]

This has probably been covered before but how often should the plugs be changed in the ETECs. Regular service? Between services? # of hours?

I've got a '05 200 HO. Runs fine since last service. Just wondering.....

Thanks!

[ChampioNman]

Check them every 100 hrs more often if you idle a lot.