I've created a landscape scene where I've painted (quite a lot of) grass and a few trees. Is it best to leave it as paint for rendering or is it best to convert the paint to poly?

So far I tried rendering a 20 sec scene at 720 x 576 24fps at 300dpi and on my 2.6Ghz Intel dual core machine with 3GB RAM it's going to take about 20 hours to render currently! I got an error after 8 hours yesterday so I have to try again! grr!

I like the quality that the paint has given me and I've tied bump mapping the plane but I don't like it. As it's for a final year project too, I want it to be the best it can be but I want to cut down the rendering time.

Any suggestions please (In plain English as I'm still learning!)

Thanks a lot
Mike