It's all perspective I guess. Personally if i can afford them (meaning save up to buy them, pay the upkeep, and still be able to afford colonizing new planets) then I see no reason not to get them. They may be less than a days increase to some, but that's still a weeks increase you didn't have before installing them.

Colonizing planets gets pretty expensive, that's why the cost is never worth it.

At the point it gets to be too much, the costs to colonize a planet are far beyond the additional upkeep of a quasi. Meaning adding quasis would only add a few hours to a day to the time needed to build up the credits for a planet, which to me, is an acceptable tradeoff if you aren't trying to take tons of planets at once. And since I'm growing increasingly picky in what I take, I suspect that I will hold out for the best planets I could find, and a couple hours won't matter anyway.

Again, just a matter of perspective.

ive finished planet structure research, scanner research, shield research, hull research, and weapon research. got all my best hulls in. 1 scanner, 1 shield (limited by size), and im rank 383. 3735 attack 4446 defense, 11800 hull 2800 shield.

What's that in reference to? Seems off topic unless I'm missing something.

Here's my understanding: I don't have QCBs but from what I've seen here and other threads they are extremely costly for such a small amount of attack that could be fixed with a bunch of prisoners and rank ups. Those extra creds could be used for other things like one day beating Mento in a bid for a dyson
Most stats on your ship can be replaced by rank points, QCBs are like a shortcut but the shortcut doesn't really go far once you can actually afford them.

True, to an extent. This is also true if you take it to its maximum logical conclusion, being don't install anything that can be created through artifacts, because credits are more important. Meaning no attack, no defense, no hull, and no shield. While clearly this is an exaggeration to prove my point, the fact is that credits can only get you so far with a ship valuing the "intangible" of wealth over the combat ability of the ship itself. Everyone has to develop their own line as to when credits are more valuable than a certain boost you would gain from the modules. And while QCB are admittedly very expensive, for a disproportionate bonus to attack, for many end game players the boost is still worth it. Just depends on where you personally draw the line.

ive finished planet structure research, scanner research, shield research, hull research, and weapon research. got all my best hulls in. 1 scanner, 1 shield (limited by size), and im rank 383. 3735 attack 4446 defense, 11800 hull 2800 shield.

Yeah, also the deck space that would've been used for it won't exist, lowering your damage cap... I think...
Meh, to each his own. I'll only do the tier for the minefields.