Persistent data get missing

I have implemented the PersistentStateComponent interface to persist the plugin setting data. Everything works fine as expected but if I keep the IDEA open for a long time (ex: more than 8 hours).  PersistentStateComponent class values returns null when the getter methods are called. Need to restart the IDEA to make it work again.What is the possible cause for this issue

IDEA versions : 16.2.4 

Following is the implementation

@State(name = "mySetting", storages = @Storage(id = "mySetting",
file = "com.mySetting.setting.xml"))
public class PreferenceManager implements PersistentStateComponent<PreferenceManager> {

public String credentialMap;

public void setCredentialObjectValue(String objValue) {
this.credentialMap = objValue;
}

public String getCredentialObjValue() {
return this.credentialMap;
}

@Nullable
@Override
public PreferenceManager getState() {
return this;
}

@Override
public void loadState(PreferenceManager preferenceManager) {
XmlSerializerUtil.copyBean(preferenceManager, this);
}