i also thought the renders where becoming slow due to the amount of content i had in the library? i read somewhere this can affect the renders. so I tried to delete the contents I didn't need no more but then my whole file went missing lol. so I just deleted Daz and haven't touched it since that issue.
It's more the amount of content within the picture, so 3 G8 figures in some complicated outfits, hair, personal props etc, plus a heavy background, will stretch the limits of your machine, and to be honest, 2 hours isn't a long time, in the bad old days of pen & paper, two or three weeks was a normal ''Render Time''.....You can also use the time to edit your content, don't upload things you've never used, or no longer use...The pixalation can be fixed, PM me if you want to...