How long would the rpr syphilis test be accurate after infection. would it be accurate between 1-2 years after exposure or is it less reliable then?

NEVER realiable: The RPR is never a "reliable" test for syphilis. It is only a screen. If you have any concern that you have syphilis, get with your physician for more accurate testing.

Very reliable: First, RPR is no longer the usual first blood test for syphilis. Most labs now start with an IgG ELISA. Either this or RPR is always positive within 6 weeks. In other words, a negative test more than 6 weeks after the last posssible exposure, including 1-2 years, proves you do not have active syphilis. However, a positive results isn't necessarily reliable; positives require confirmatory testing.