I agree about the lag and the mob disappearing. I have strong wifi, so that's not the issue. It only seems to happen when I am using an elixir. I'm able to run through an empty street, but have to turn around and wait for the mobs to appear. So, bad wifi doesn't make sense. As far as being warned about the buff wearing off, it doesn't bother me unless my time has been wasted waiting for the mob to show up.