Wondering because with each update, I have to travel further and further. Also if I collect a lot of a specific resource (like those two tall flowers) I need to travel further to find more, but how do I actually know that I'm going beyond what I've explored already?
I'd need a ton of maps and an enourmous mapping room
Err, yes. I guess it depends how many full scale maps you're talking about. I generally always have a map wall which is five by five maps giving you an area of twenty five maps. That's a pretty big area and I find it hard to imagine running out of any resource in that size area. Another thing you could do is carry some blank maps and if you open it in an area you've been before it will paint the map in so you'll know you've been before. If it doesn't paint it in you'll know you haven't been before. Carrying spare maps isn't really a big deal they're stackable, and if you have an ender chest or shulker box, no problem!
If you're in the biome where you got the flower you can use bone meal on the ground and there is the possibility that it will make more of that flower. No need to go find that biome that hasn't been explored.