I've been taking it for two years - no-one has ever mentioned any problems taking it long term. I would if I were in your position, just in case of any accidents. Then again plenty of women get pregnant unexpectedly and take it from the time of their positive test so if you don't want to don't get hung up thinking you should.
No probs with taking it long term, it is in multivitamins such as the 'Wellwomen' ones anyway... Although unless you are actively TTC I can't see the point really, condoms are very effective if used properly so unless you are planning to have an 'accident' I wouldn't bother