F# Type Providers very very slow build

Try using the LocalSchemaFile attribute for the data provider. This points to a .csdl file that is used to generate the types. You can have the type provider update this file by setting the ForceUpdate attribute to true. To run from a cached schema simply set ForceUpdate to false. Here is how I do this with the SqlDataConnection provider, which is very similar to the SqlEntityConnection provider.

type schema = SqlDataConnection< LocalSchemaFile = "Schema.dbml", ForceUpdate = false, ConnectionString = @"Data Source=<insert your connection string here>" >