Not that I mind a long game, as I would play typical 4X games for up to 8 hours a day. But I would like to play in a much larger galaxy but can't see myself playing a SP session that would last weeks for one game.
I've had some medium maps last 8-10 hours, and large/huge take considerably longer. I think a large variable to this is how well populated the randomly generated map is. If you get mostly planets in your area and your opponent is left with asteriods and gas giants, you're going to trounce them much faster. Try soem of the premade maps and take on medium or hard AI's, and you'll find the game takes a lot longer on even a small map.
Also the type of AI you choose can alter the game time drastically, the economy or researching AI is pretty weak on the O and D, while the Agressor and Fortificator is much better at getting out there and taking planets/making themselves a problem to your empire.
* Does it make sense to slow down pirate attacks up to 30 minutes, or eliminate them altogether? I would rather focus on the enemy races than the pirates, despite the experience benefits.
I've slowed them down to 30 mintues in one of my mods, (and the slow pirates mod makes them about 20-25 minutes apart) and found they were more of a minor pest instead of the semi threatening annoyance they are normally.
If you do slow them down (default is 10 mintues I believe) then increase by 50% (or double) their power/# of ships etc.. for every 10 minutes you slow them down by. (2-3x as powerful every 30 mintues still makes them a danger but not the "every 5 mintues pain in the ass annoyance" they are now)
* The game seems to take a long time to play, though I understand that aspect is part of its charm. Is the better way to speed up gameplay by making resources easier to acquire or by making ship weapons more powerful than they are, or does some other change work better without breaking gameplay? Perhaps I should reduce the shield strength somewhat, either shield mitigation or regeneration
I found a better change is to reduce the cost (in mineral and metal not credit) for the research requirements that pull in the crystal and metal so that you can boost a sagging economy easier. (after all if you're poor on crystal, trying to pull in the 100+ crystal to upgrade crystal harvesting is going to be a pain in the ass) Also adding 2-3 more levels (that cost considerably more each time) to the crystal/mining research helps a player with poor crystal/metal resources compensate for the loss. (especially on random maps with random resources)
But like falloutboy said, this can turn make things faster paced, although with this method the time it takes you to research the tech helps alleviate this somewhat, and the extra resource income helps in late game on bigger maps when most of your economy is tied up in fleet maintainence.
I never really bothered with the black market, since in single player the AI seems to ignore it entirely, so you wind up paying through the nose for the needed crystal/minerals over time. (400-500cr+ per 100 crystal/metal? Oucha!)