I'd do it a tad earlier to be honest.
From both a historical and balance standpoint what you really want to strive for is a gradual and logical progression of the scope of the game as the game marches on. And one that fits in nicely with existing game mechanics. And in part this is what you have already built the framework for.
In the early eras you are already rather limited as to how far you can go. Before you hit about medieval stuff stuff like stability and

due to size and upkeep penalties really limit your expansion distance making exploration beyond that just gratuitous. Thus the game tends to naturally be restricted in scope during these eras. You might have managed to meet an empire that's on the opposite side of your continent by having your scouts wonder around for 50 turns through endless no mans land, but it's gratuitous because there is nothing you can do with that contact.
By the time you hit medieval though you already have the techs to trade with people along coastlines so long range trade becomes a thing making long range contacts reasonable. And at the same time you have the ships, the cavalry and the infrastructure to actually go and fight across much longer distances. Not to mention the empire size. So those
Spain meets Russia sort of contacts start playing a genuine part in the game.
At the same time, from a balance standpoint pushing the limit removal down to the Renaissance would give you a long blank spot in the medieval period where you've got nothing to do even though by all other mechanics you should be able to, followed instantly by a sudden and overwhelming influx of new options in the era that would give you both inter and intra continental expansion. It would be much more balance friendly to instead divide those up between the two eras so as to produce a more gradual game progression.
So really you want to set things up to form something kind of like this:
Ancient - Set up and survive against barbarians and beasts
Classical - Early religions, early expansion, small localized empires interacting within small localized areas. Civs tend to interact in regional clusters the size of modern nations, with the clusters occasionally interacting via the very borders.
Medieval - The strongest empires in each cluster grow out to conquer or subjugate their neighbors and become big kingdoms vying for dominance over the continent.
Renaissance -These new continental powers start exploiting sea travel to seek riches and allies abroad in order to get an advantage over their neighbors.
Everything leading up to Future - As travel becomes easier and more accessible you get empires which start to dominate their home continents leading to titanic struggles culminating in a decisive war or two at the tail end of the modern era.
Future - Continent sized empires fighting each other for dominance over the world.
At least that's how I see it. So I would put the end of the land distance limit somewhere smack in the middle of the middle ages.