Arma 2 Operation Arrowhead - Possible Loss Custom Mission

/*
*     Possible Loss
*       by Tommy
*     Defend to survive!
*/

_spawnMarker1 = getMarkerPos "spawn1"; // Above
_spawnMarker4 = getMarkerPos "spawn4"; // Below
_wayMarker = getMarkerPos "way1"; // Centered (air field)

_unitName = "Mi17_TK_EP1";
_pilotName = "TK_Soldier_Pilot_EP1";

_heliSpawnCount = 0;
_grp1 = createGroup EAST;
_grp4 = createGroup EAST;

_ammoMag = "2000Rnd_23mm_AZP85";

_cleanArray = [];

while {true} do
{
    // Increment the counter
    _heliSpawnCount = _heliSpawnCount + 1;

	// Create the first helicopter for the first group
	_heli1 = createVehicle[_unitName, _spawnMarker1, [], 0, "FLY"];
	// Etc..
	_heli4 = createVehicle[_unitName, _spawnMarker4, [], 0, "FLY"];

	_cleanArray = _cleanArray + [_heli1, _heli4];

    _pilotName createUnit [getPos _heli1, _grp1];
	_pilotName createUnit [getPos _heli4, _grp4];

    {
        _x moveInDriver _heli1;
        _heli1 doMove(_wayMarker);
    } foreach units _grp1;

    {
        _x moveInDriver _heli4;
        _heli4 doMove(_wayMarker);
    } foreach units _grp4;

	switch (_heliSpawnCount) do
	{
        case 30:
		{
		    hint "Lagging yet? Clean up time!";
		    {
		      deleteVehicle _x;
		    } foreach _cleanArray;
			_heliSpawnCount = 0;
		};
	};

	// Check ammo, need lots!
	if (vehicle player != player) then
	{
	    _ammoCount = player ammo _ammoMag;
	    if (_ammoCount < 500) then
	    {
	        vehicle player addMagazineTurret[_ammoMag, [0]];
	    };
	};

	// Need to pause spawning so they can get moving without crashing
    sleep 15;
}