How to register asynchronous request events?

I am trying to optimize JS code of my portal. I register request events in the following way.

function pageLoad(sender, e) {
    //if (e._isPartialLoad == false) {
    Sys.WebForms.PageRequestManager.getInstance().remove_initializeRequest(InitializeRequest);
    Sys.WebForms.PageRequestManager.getInstance().remove_beginRequest(BeginRequest);
    Sys.WebForms.PageRequestManager.getInstance().remove_endRequest(EndRequest);
    Sys.WebForms.PageRequestManager.getInstance().add_initializeRequest(InitializeRequest);
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequest);
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequest);
    //}
}

Should I call remove/add methods when e._isPartialLoad is false so that it only registers once in page life span?

If there is postback from an update panel, will it remove event association?

Thanks for help.