6 hours? So you walked over to the next neighbourhood and back.
OK, seriously, the only way to make money exploring is to pick and choose what you scan, and to know where to look for valuable things.
Black holes and neutrons are the best way to make credits, but you need to know how to find them. As for anything else, Metal rich and High metal content planets are only worth scanning if they are kind of nearby, as it takes a huge effort to break away from the gravity of the main star. I'll make the effort to scan them, personally, but if you are purely after the creds - if the closest one is not within 200Ls, skip it.
Finally, water worlds, ammonia worlds and earth like planets will make a lot of cash, too, but it's kind or random where you will find them.
Jovials and regular stars - if you can scan them from the main star location, do so, otherwise, skip them.
Rocky and ice worlds - don't bother.
My method of exploration is basically, to drop in to a system and see what's there. if I find anything interesting at all, I'll scan the whole system - unless the rocky and ice worlds are really far out, I may skip those.
Wild cards are terraforming candidate planets. You get a nice bonus, and almost all planet types have th epotential, except ice worlds and (probably) ammonia worlds. I say probably, because I swear I came across an ammonia world that had "this planet is a candidate for terraforming", but, I didn't know how to take a snapshot then, and apart from the "Huh? Really" response in my head, I moved along. Of course, I could have mixed up what I saw, and being very close to Sag A (with all the gal map issues) I'm not going back to look for it.
There are "zones" where planets are likely to be in a terraformable zone, but that doesn't guarantee anything, just a better chance. I've found plenty of terraforming candidates and a few earth-like planets orbiting neutron stars, too. That's one heck of an o-zone layer they have, there!
Anyway, for me it's about finding the unusual - earth-like worlds orbiting neutrons, for example. Amazing vistas near a nebula, checking something out just because it looks to have a grumpy face on the system map...
I'm still hunting for an Earth-like or terraformable orbiting a black hole. I doubt it exists, but if it's out there...
Z...