Thanks for the reply. What I meant with a "snapshot allowed to run for weeks" is a snapshot taken some weeks ago, that will generate double activity. Every change in the source database will also cause activity in the snapshot. Therefore I wonder if you should be careful with snapshots. Once you don't need a snapshot anymore, you should probably delete it immediately, right?

It's a fact that it will cause impact on performance. But a 'normal' server should be able to handle that, so that mustn't be a problem.