lower ram-usage with vector displacement

[skogskalle]

Ive been playing around with vector displacement lately and i find that to get a good quality on my displacement I often have to use a edge-length of 1, atleast for closeups. It looks awsome and renders pretty fast but uses a huge amount of ram... like 3-4 GB for rendering a 2x3 m furry carpet in an interior.

Would it be possible to make it use less ram at the price of longer rendertimes? Or maybe this is possible now and i just havent found the setting for it??