Hi mate, I don't bother with incrementals, they are too much bother. I just do a complete backup once a month, it saves all sorts of complications. I do mine at the beginning of each month and keep this plus the last month, and delete the one previous to that i.e. backup June, keep May, delete April.
I do, however, make a separate copy of My Documents via copy and paste so I can easily get to it if needed.
48gb in 4 hours is 12gb per hour which seems a tad on the slow side but it's in the ballpark . I use Acronis 9 and it backs up and verifies 14gb in about 50 minutes or so.