'Best Practice' Question

I have 3 drives (C:\, D:\, K:\) backing up to a 2 TB External drive J:\

My backup definition is: incrementally with a new monthly base. This results in a restore point consisting of 750GB for the 3 drives combined.

As I understand things, with a 2TB drive, you're limited to 1 recovery set; right? (I can't choose 2 sets to be saved because that would require enough space to hold: 750GB X 750GB + the newly completed 750GB one- right?).

So, now the question becomes: is 1 set, verified, good enough; or should I acquire a 4TB drive that will hold 3 recovery point sets? I realize that this is kind of a rhetorical question, but thoughts?

Thank you