Badblocks run time (Dreamplug + USB)

So I put my hands on two seagate external hard drives (2T), and I want to use them as a raid device. Prior using the drives, I like to run some checks on them, to see if they deserve my data to be put on them. I ran badblocks on both drives at the same time. I don't think, that it has any impact on the speed. To record how much time did it take to run badblocks on 2T drives connected through USB to my Dreamplug, I captured some outputs:

root@plugged:~# badblocks -b 1048576 -w -o badblocks.W1E2JW11 -s -v /dev/sdc
Checking for bad blocks in read-write mode
From block 0 to 1907728
Testing with pattern 0xaa: done                                
Reading and comparing: done                                
Testing with pattern 0x55:  77.39% done, 92:31:15 elapsed

root@plugged:~# badblocks -b 1048576 -w -o badblocks.W1E2GMMM -s -v /dev/sdd
Checking for bad blocks in read-write mode
From block 0 to 1907728
Testing with pattern 0xaa: done                                
Reading and comparing: done                                
Testing with pattern 0x55: done                                
Reading and comparing: done                                
Testing with pattern 0xff: done                                
Reading and comparing:   2.04% done, 172:41:55 elapsed

Badblock with these parameters tests 4 patterns: 0xaa, 0x55, 0xff, 0x00. The latter output shows the time required to get to the read-back phase of the second pattern. So let's say the read and write takes up around the same time, meaning we have the time for 5 iterations:

5x = 172
x = 34.4

And for doing all the 8 phases, you will need 275.2 hours, around 11.5 days, let's say 12 days. I am not sure, that this is the most economic way of doing it, because the drives are consuming a lot power, so it might make sense to drive them as fast as possible with a more powerful machine.