demosthenes: Two years is extreme and sounds like another attempt at age-gapology.
1] If a girl comes back from seminary with pie in the sky ideas which are not ideas she had prior to her year in seminary and are diametricly opposed to her upbringing, by all means let her wait until she lands. Reasess her ideas in six months to see where she is holding on the issues. Otherwise, she will either marry quickly and wake up to reality too late, or get engaged, freak out, and break up.
2] If a girl comes back with the same hashkafos and didn’t monumentaly change her overall worldview on basic Jewish living, and SHE chooses to date there is no reason to hold her back. Judaism doesn’t practice MARRIAGE CONTROL, no matter how great a “crisis” might be.