Doctors say long exposure to hpv viruses is needed to cause cancer of the cervix or vagina.what is long exposure here? (for example,if hustband and wife have frequent sexual intercourse, is this also a long exposure??

Length of exposure is not necessarily the issue, rather the pathogenicity of the virus and your immune response to it is. If you are worried about cervical cancer, you should get pap smears with reflex hpv testing. Some HPV serotypes are more likley to cause cervical cancer than others. For instance types 6 and 11 lead to warts while 16, 18, 36, 54 and others are more likely to be cancer causers.