When the edited changes will appear permanent

All changes that you upload are instantly and permanently in the map (map-database). For renderings it depends how often the renderer imports data from the main database (and how frequently it re-renders the map).

Mapnik generally (if there is no problem) takes around one minute to get aware of the new data and some more minutes to render the high-zoom-tiles (z15-18). There are different mechanisms in place to deal with tile-expiry (re-rendering of old tiles). One important factor is if the map is actually looked at.

Generally this depends on the map, the activity in the system and on the zoom level. If you added something that is rendered (i.e. there is a rendering rule for it) it will usually appear shortly (some minutes) afterwards on the main mapnik map and with a little delay on tiles@home/osmarender. But sometimes the servers suffer from many parallel requests and might no be able to cope with all rendering request.

Low-zoom-tiles are re-rendered less frequently because they take far longer to calculate (they contain more data). I might take up to a month or so until you can see you additions in lower zoom levels.

If you're under the impression that your tile somehow skipped the re-rendering process (this happens when the rendering queue is full), you can also manually request a re-render by calling the tile and add "/dirty" to it like this: http://tile.openstreetmap.org/7/63/42.png/dirty

You can see the current status of the mapnik rendering server here: http://munin.openstreetmap.org/openstreetmap/yevaud.openstreetmap/index.html#renderd

I did some edits 14 hours ago and most of it appears at all zoom levels