simple one - web or service reference global (at page) variable on each page load

Hi there,
Just a (hopefully) quick one:
is this bad/good/acceptable?
    public partial class UpdateDetails : System.Web.UI.Page     { IWebService myWebSvc = new ServiceRef.WebSrv(); // instantiate a proxy, but may never use it     protected void Something_AnEvent(object sender, EventArgs e)         { var stuff = myWebSvc.GetStuff(); //call the service            &n ...