I had an e-mail from a regular customer recently about whether turning their cooker off for the summer would cause it to rust. The truth is that yes, condensation can form and rust occur.
The solution is simple. Leave the doors and lids slightly ajar to allow air to circulate (a pencil under the lid rim works great!) and lightly oil the hotplates and expansion rings around them with seasoning flax oil, or any light oil really, on some kitchen roll!