I've got some nice portraits with my 2x3 Speed and a 105. But if you want a longer lens, why not?
FWIW, the longest non-tele lens that will work comfortably on a Century (I have one too) is probably around 180 mm. I know people who use 203/7.7 Ektars and 203/7.5 Raptars on their Centuries, but they aren't all that happy with running the front standard nearly all the way out. In "original issue" lenses, the 203/5.6 and 250/5.6 Wollensak tele lenses (Tele Raptar on Wolly dress, Tele Optar in Graflex) both are comfortable fits on the camera.
In other words, there are many lenses out there to choose among. If you want a longer lens, why not?