Yes on all you said, I am at the point that my bass sounds really good, stays in tune, I am fine with it. I cant justify spending $5000 for a bass that sounds 5% better than my $300 bass. Also does not stay in tune any better than my current bass does. Would I like a more expensive bass? sure, but I only gig 1 or 2 times per month. actually how much better is a $5000 bass compared to a good $300 bass other than the finish? 16 times better? compared to what I have seen over the 25+ years of playing, I would say 1.5 times better, again, mainly the finish..
I think it depends on the particular bass, but I've had better playing, cheap instruments than a lot of really high end ones. Just depends on the particular plank of wood you get.
There is something to be said for the hotrodded, cheap bass though..
This may sound odd, but I started in high school orchestra. In that setting, practice was indeed all the practice I did - I played upright bass and didn't have one at home, so the only practicing I could do was in orchestra class. Then I had a long layoff (1973 to 1997).
When I joined a surf band 24 years later, I didn't realize that I needed to show up to practice with my parts already worked out. That just hadn't been part of my training. It took me a while to figure out that I had missed something, and I needed to do work ahead of time.
Now (although my practice habits are still weak) I know that I need to work out everything in the set before showing up to practice, so that we can concentrate on working out timing and any odd parts that need to be refined in a group setting.
Some other things I've learned:
I don't have a "tone." I can always get a sound I like out of any amp and bass I've owned or used at a jam. All I care about is getting a sound that's pleasing to me. It can be different every night.
My ears aren't what they used to be, so I don't hear many subtle differences between basses. I often wonder what people are talking about with some of the differences they claim to hear between basses (especially with differences in wood and pickups.) I'm still not sure how often they're hearing something I don't, and how often they're simply describing "psycho-acoustics" that are all in their head.
There are definitely differences with tone in a lot of that stuff, however.. most of the time, whomever is listening to our music, besides us... just doesn't hear it.