[Closed] How long for a test drive?

When buying a car how long do you test drive it for? I have a relative whose a mechanic that will look under the bonnet and kick the tyres for me, but I'm a bit stumped by the test drive lengths. Showrooms seem to like you to go for about 2 miles (on a route they've picked) and seem offended if you ask to drive it for a bit longer or in towns. Maybe it's my rubbish driving that puts them off? I've not brought a car before but I expect a more substancial drive in it before parting with a large sum of money. I'm new to this driving thing, am I just being fussy? If I don't get a proper drive I've just been walking away.