Points for limited theme selectors

So I’ve been saving diamonds for a while (currently at 8k) ready to spend on a limited theme. I’m planning on buying lots of the 150 diamond card packs, and using the points I get to to select whichever cards I don’t get prism of. I was wondering, can I save all of my points (e.g. 250 x 8) until I’ve spent all my diamonds? Or do I need to select a card once I’ve reached 250 points. I hope this makes sense, it sounds kinda confusing lol. I just want to use the selectors at the end when I know which members I didn’t get prisms of.