Like others have said, your experience is not necessarily typical.
In these times of belt tightening, dealers should be looking to improver their efficiency, but also to offer additional services to make their offering more attractive.
For example the garage that services/repairs my car, will actually collect it leave a courtesy car. Take my car away and do the work on it and return it to me and exchange it for the courtesy car. This is not a new car, and what I pay for the service I judge is worth it to me.
How about dealers collecting caravans from their customers, and enhanced offer which i am sure some would find very attractive.
Unless there is other work to be carried out such as repairs, then there is no need for a dealer to have your caravan for more than a day. The service work is neither complex nor especially time consuming for trained personnel, and the parts are items any good dealer should carry in stock.
Its not in their interests to have a customers caravan at the centre for longer than is necessary, it takes up space which could be put to more productive use, it takes time and man power to shunt the vans around the storage yard so they can get at the next one, having the van on site for so long increases the chance it will be damaged whilst in the dealers care, and worst of all it slows cash turnover.
Tell your service centre you are unhappy with the turnaround time, and that as a result you are considering alternative arrangements, it might spur them onto better performance.
I suggest you look for an alternative dealer or even consider using a mobile engineer - quicker and more convenient, and often cheaper.