Tough question, as far as I'm concerned, since it really depends entirely on what your "goal" is in the game, as in "when have I 'beat' the game/'won' the game/done all that I can in the game".
As such, it's highly subjective, as is anything and everything I write in the following. All of it works for me, but that doesn't make it any more or less "valid" (how I hate that word) than anybody else's opinion.
I play this game, indeed any game, to have fun and to feel that I'm "working" for something. However, my idea of that "something" I'm working for is most likely very different from anybody else's, and that's fine. I get the feeling, and I might be wrong, that the current, contemporary idea of what constitutes a goal in any game is "get to the end game as quick as possible. It isn't for me.
But, with that in mind, what are MY "goals?". Quite simple: to get to the "next ship." Or to get to the "next upgrade."
If my goal was "to get to the point where I can own an Anaconda", my ideal credits/hour would be much higher, because getting to that would be all that I cared about. Or it could be "owning an Fleet Carrier", it really doesn't matter, except the "ideal" Cr/hr goes up the more expensive my "goal" is.
I started back in the beta (oh dear, here goes another "back in MY day" post

, but bear with me, it's relevant), and my goal was, and remains, as I said, to get to the point where I can buy a better ship. I couldn't care less about getting myself an Annie back then, except to the point where it would be awesome, but it was way out there, in the future. I didn't need it. I just wanted to upgrade the crappy modules on my Freewinder and then, when I'd done that, I wanted an Eagle. Then I wanted a Viper. Then I wanted an Adder. Then I wanted a Cobra. That was my focus. It was hard and it took a long time, but every single time I'd scrimped and scraped to get a better module or a better ship, it felt like a victory and it made me happy. I didn't care a whit about calculating how long it would take me to get to the vaunted Annie, I just cared about getting to the next step up the ladder.
It took me a long time to get into that shiny new Cobra Mk. III, actually not so shiny when I could first buy it, because I didn't have enough to kit her out with anything beyond the crappy stock modules, but, as with all of the previous ships, just hopping into her and taking her for the first ride was the biggest thrill of all.
Fast forward. I took a long break from the game, not because I stopped enjoying it but because RL and other games caught my fancy and then I came back. And suddenly realized that the Asp that would have been my next project was but a few hours of play away. And then, a mere tens of hours after that, I'd not only fully A-rated and engineered my Asp, I had more than enough money to get the Python, something that used to be a long term project. And now I can buy any ship in the game except for an FC without even worrying about my credit balance. I can go straight from owning a Python to buying literally ANY ship in the game and A-rating and G5 engineering it, almost instantly.
It took me months, almost a year, to get me into that Cobra, and I enjoyed every second of it because I got to learn how to fly every single one of the ships along the way, enjoyed every little upgrade, best time in the game for me. And then I got back after the hiatus and got to "money is not an issue" in less than two months. I threw out a quarter billion to transfer my Krait from the Bubble to Colonia because hey, whatever.
That hasn't improved my enjoyment of the game. I can't say it's significantly reduced it either, I'm still here, aren't I?
But I just don't care as much anymore. What's my "ideal" Cr/hr rate?
I'd be fine with pretty much what it was, but that's only because I intend to keep playing it for as long as it takes. I don't have an urge to "finish" the game, as a matter of fact I'd rather not finish it ever, but I completely understand people who measure their success by how quickly they can get to the "end." I don't agree with that approach, I like to get as much out of a game as possible, but I understand it.
So if the metric is "how fast can I get an FC?", then it's completely different from "how fast can I get the next step up the ladder."
And that's subjective. There is no right or wrong answer to that, I just know what works for me.
Enough rambling, I'll see myself out.