What changes are you referring to specifically? With EF, there's an Update Model feature that brings in changes without redoing the entire model. However, if you haven't renamed any of your tables, columns, relations and so on, redoing the model may be quicker.
But also, I'm just afraid of a lot of junk auto-generated code laying around.
Not sure what you mean by this.
If you want to rename code, you may want to look into Refactoring tools such as Refactor! from DevExpress or Resharper. They let you change / rename code (and do a whole lot more) through projects without breaking dependencies.
Finally, larger applications tend to break less if you have a high separation of concerns. So, if you have SQL Code directly in a SqlDataSource control, things will break in many locations when you change the database. If you abstract data access away to a separate data layer, you can minimize the places where you have to fix or change anything.
But I guess it all depends on the type of changes you're referring to. Changes to CSS or your data model require different handling than changes to the model, the UI, your client side validation and so on.