I am having trouble booking my caravan for it's annual service, what timescale is acceptable?

For each annual service, we state that the van must be serviced within the generous time window of 90 days before each anniversary of the original date of purchase, and 60 days after. For the Supersure Warranty the third service must be completed by the third anniversary of the date of purchase and for the body shell body shell integrity guarantee by the sixth anniversary of the date of purchase.