Insurers vary, some cover holiday statics up to 20 years in new-for-old - it is worth while comparing the cost of the premium between new for old and market value, as it may not be much - I have a feeling that the cost of the van itself makes only a small park of the premium, it is all the other bits (public liability, contents, site clearance cover, etc) that build up the cost.
The most important thing is to make sure that (especially if you are on a park) you are covered for site clearance in the event of a disaster.
If you are planning to rent out your van, then make sure this is included.
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