Late pledge is usually open for about a month, if I remember right from CMON's past kickstarters. But it's really up to them. I'd bank on at least a month. So if you need to save up to get more stuff, you should have at least that long.
It's also worth keeping in mind that it usually takes a few weeks before Kickstarter releases the funds to CMON (I think that's how it works). So you might have closer to at least a month and a half to scrounge a few more dollars and cents.
I know because I late pledged the original Z:BP KS, and got everything. In addition, I got it at the same time as all the other backers because I filled out the pledge manager before the pledge manager cutoff date (which, for Z:BP GH isn't even out yet).