I'm currently building the UI for a webapp where users can refresh various bits of content. The speed of this refresh depends on the type of content. In most places this is a very quick operation (max 1 sec). However, certain panes take dramatically longer (4-30 seconds, average 10 seconds) depending on the amount of data being dealt with.
The difference in response times is due to the system either looking in the database for the latest piece of content for quick panes, or generating a new piece of content in slow instances. A pane will only ever have one of the two modes, never both.
The question is, should I use two different refresh icons for the different speeds, or the same icon across the system? The separate icon could be the original refresh with a small clock/hourglass added to it.
It's worth noting that when the user uses the slow refresh, we use a (non-blocking) message to inform them that fresh content is being created and it may take some time. As we don't know the size of data in advance, and the data acquisition is the slow part of the system, we can't really use a % done indicator.