Changing strings

I know how and have changed my strings several times but I do have a question. My fretboard needs a cleaning and oiling from severe use. I have heard both sides of the argument but I still need advice. Is it ok to remove ALL 6 strings at once to clean the fretboard? This guitar does not have a dual action truss rod and I don't want to have to shell out for another setup. Any help would be appreciated.