But that's if it's a precise occurrence- such as, closest the Earth ever gets to Venus [most furthest]. Earth's aphelion or perihelion, of course, occurs every year and as far as synodic location it is about same each year- though it does have precession over longer period of time.
[most furthest] should have been [or the most furthest].

But I noticed I didn't address your point very well. Yes if you looking for the lowest delta-v to Venus or anywhere then you will need to wait a long time, but getting the lowest delta-v isn't really what I'm interested in. Instead I'm more interested getting to Mars or somewhere else quicker and having more windows.
But infrequent windows could useful, for instance, suppose you had Earth/Venus cycler which bounced back forth from Earth to Venus but every decade went to Mercury or Mars or both. Or similarly, one send spacecraft on fairly long trip- say get two gravity assists off Venus than hitting earth for final delta-v assist [like Cassini mission did] but instead go to Mars. And when it's near earth you could send crew to it. This would require a lot propellent to brake at Mars, but it's better than burning fuel to get to high velocity and then using fuel to slow down [you get your acceleration from the gravity assits- so it might take less than half the fuel].