Easy Updates Manager, with this advanced option enabled, will alert you to any unmaintained plugins in the WordPress Plugin Directory.
Check Unmaintained Plugins Advanced Screen
By default, plugins are outdated if they haven’t been updated in a year. You can change the timeframe using the following filter:
eum_unmaintained_plugins_time
An example:
add_filter( 'eum_unmaintained_plugins_time', function( $time ) {
return '-6 months';
} );