"How far back do you go before you think it's so far back that it doesn't really matter?"
I think once you get past a certain stage when details become very sparse and all you have are names and dates then you really don't learn much about people other than their names.
But, if you get your DNA tested then it can be really interesting finding out how you are connected and, for me, I find this is often what drives me to go back further, to find out exactly how we are connected.
It's really interesting going back to our common ancestor and seeing how their side of the family has differed from that point on compared to my own ancestors.
What really started this off for me was when my mum got her DNA tested and she came across a whole load of very distant (5th to 8th cousins) DNA matches who had the same surname as her mother and they all lived in the USA.
How had that happened?
So that led to a lot of work and we eventually found that they were related as about 8th cousins. It turned out that back in the 1690s a couple of cousins in that family went over to America and became tobacco farmers. Our side of the family stayed home and worked as farm labourers.
So, the whole thing driving going further back was to find out how come we had so many distant relations in the USA.
We found something similar with my dad as well, although much later. In the 1860s a family member went off and joined the Mormons in Utah. We now have so many relations who live in Utah (and, I guess, are Mormons).
We also had many other relations who went off to Canada, Australia and New Zealand throughout the 1800s
"Obviously you don't need money to be interesting but it just means there are a lot more records available so easier to follow."
That was the case with the family that went over to America in the 1690s, they were part of a wealthy and very well documented family. My ancestors were the sort of seventh son of a seventh son so they never saw any of the money.