What should I do about the crimson/hallow?

[Clockwork Alpha]

The crimson is consuming at my world at a rate that is very fast even after I have killed Plantera.

Should I hallow the world or just keep purifying it?

Also, my base is relatively high in the air, to the point where from the bottom of it you can't see the ground.

 

[The Mythical Dagger]

The most effective, but least efficient, is digging hell-evators that are four tiles wide, at both ends of the spreading biomes. The hell-evator can be left as air, or filled with non-convertible blocks (i.e. Snow or Clay). This way, the Crimson is still in your world.

Otherwise, I suggest cleansing the world over and over, since that is the easiest method, but tedious.

 

[rubeszilla]

Let it grow. You only really need to keep it away from your base, so clentaminate some Hallow around your base. You'll also need a tiny bit of forest for werewolves (and peace ). The rest of the world can be overtaken. In the extremely unlikely event that your jungle is overtaken before you "finish" the game you can simply create your own, as The Magic Dagger said, by making a 4 tile wide barrier of non-corruptable blocks around it.

 

[Clockwork Alpha]

Now with a poll. Please vote.

 

[malakhglitch]

While I voted for preserving the jungle, I do recommend making hellevators. If your Crimson is encroaching on the jungle, you might want to make a Hallow between them as a buffer.

 

[Prism]

It may be too late for this, but I always build an underground shield of wood that surrounds my base, so that no hardmode biomes can get in.

If it is too late, I would just hallow the area around your house. Mobs don't spawn around NPCs (under normal curcumstances), so not much will change.