Manuel,
I'm having all sorts of condensation issues on the sensor of my brand new 383L+. It appears that the humidity is controlled by a desiccant plug that needs to be recharged or replaced periodically. My camera is 4 months old so I would probably say that the desiccant needs to be replaced every 3-4 months. I recharged the desiccant about 12 hours ago and I'm waiting the suggested 24 hours to see if I still get dew. I am also trying to get a good supply of desiccant for future replacements.
Andy