Need "Help" in coding "trail"

Code (open) Code (close)

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
if (cmd.getName().equalsIgnoreCase("trail") && sender instanceof Player) {
Player player = (Player) sender;

if (args.length == 2) {

if (args[0].equalsIgnoreCase("hearts")) {
if (args[1].equalsIgnoreCase("on")) {
EntityEffect hearts = EntityEffect.WOLF_HEARTS;
player.playEffect(hearts);
}
if (args[0].equalsIgnoreCase("off")) {
// Remove the current effect
}
}

What I would like to know:
*How would I remove the effect using the command: /trail off
*Did I do the command correct to do:/Trail hearts
*How would I change the time that the particle stays there till it despawns.

-Thanks! Iou one.