I have a Dexdrive, so can I make my RPG as long as I want, or am I limited by how much I can fit onto two memory card?

Yes, you can.

You can only have 1 system data card, but you can have infinite scenario data cards.

Actually, it's possible to have two system cards by use of a memory card trick (don't recall any game that actually uses it), but the option of multiple scenario cards is built-in. Go ahead and make the game as big as you want.

Yeah, good thing I can make as much Scenario pieces as I want. The system data worries me though....I have been simply re-copying an area just to put a new scene in there, so I haven't really used the space there wisely.

Perhaps I should invest in a bigger memory card?

That won't work. Even if you did use a bigger memory card, you'd run out of memory long before you were able to fill the card. I'd probably recommend using up your space wisely, and have those new scenes take place on the old maps. It's a bit harder keeping track of what needs to still be in that scene and what doesn't, but it'll save a lot of memory.

Besides, those bigger cards tend to blow up and you'll wind up losing all your hard work.

boy do i know it. I ended up loosing my first game to a multipage memory card when the card decided that it wanted to move on to "other things." I suspect it wanted to try being a calculator for while.

I lost all my system data. I could have rebuilt, but I said screw it.