Some competitions declare an end date which is years into the future, or even an indeterminate end date. This practice can 'lock out' the works you submit to the competition from other competitions, or from prevent other uses you require for your work for that entire period of time.
It also gives the organisations, and sponsors if are any being assigned rights to your work by the competition rules, usage of your works with all the usage rights claimed by the rules. For these reasons this practice is deemed unfair.
If you would like to know more about copyright and related rights please read our Guide to Rights and Licensing.