// First methode
private _loop = true;
private _time = time + 30;
while {_loop} do {
    sleep 1;
    if (player distance _pos > 30) exitWith {_loop = false;};
    if (time >= _time) exitWith {_loop = false;};
        /*Other condition and code*/
};

// Second Methode
private _loop = false;
private _time = time + 30;
waitUntil {
    sleep 1;
    ((player distance _pos > 30) || (time >= _time))
};