Quote - One option is if you're doing these large sizes for print, just do a test. Render at a considerably smaller size than you're attempting. Then enlarge in Photoshop (Image > Image Size > Pixel Dimensions - be sure to select Bicubic Smoother in the Resample Image options at the bottom).

I don't know what print application you're aiming at, but if it's just for your own computer printer, the quality of PS's included enlargement capabilities is probably well within the quality range you need, and will save you huge headaches in matters of render times and system resources. Within reason (trying to enlarge by 10fold isn't likely to work), PS enlargement should do for other printing applications, as well.

I have begun to do this myself, and have so far found that PS gets a very passable quality with enlargement well past 2x the size in both directions (remember, that means well over 4x actual size in terms of square inches). That's gonna do wonders for your render time, obviously, and PS can do the enlargement in seconds.

Ideally, I want to render at larger sizes and reduce; my philosophy is start at the highest quality you can. But you also have to work with the hardware you've got, and you may be surprised what you can do if you change your approach like this.

I always do high quality prints at 300dpi 8x10 for my portfolio, sometimes with my Epson photo, sometimes lab prints. I have tried 200dpi it looked like crap with the one I did. Maybe you do it different though, I render at 72dpi and just change it after - meaning 8x10 I render at 2400x3000 I don't select a different dpi. Unless you have a better way?