Leaving it single threaded (as most shell commands already are) will probably be alright as long as it doesn't take more than a few hours.
But if it has obscene memory requirements then it'll be too much for my box. I only got 9 out of 16GB ram free and I hate force-rebooting the notatether.com webserver

It uses a bunch of pipes, so the load it causes is more like 2-3 than 1. Memory requirements can be low, but it uses tmp files instead. It should be done within a few hours, and doesn't need frequent updates (once every 2 weeks will be fine).