I never buy anything from a dealer without a home demo. No demo, no sale, under any circumstances.
If the dealer requires money, either a deposit or full price, I require him to write on the receipt that this is for a home demo, to be refunded if the item is returned by an agreed specified date (usually up to 5 days). Only a few dealers have refused to go along with this, so I've made it clear that they've lost not only the possibility of this particular sale, but also my future custom.