thanks for the tips. just a few more questions:
if my threat is supposed to be that low, how am i supposed to raise defenses if i dont shoot for turret controllers and fabs? (i prioritize sniper and/or spider controllers near the top of my list)
i play with core shield generators turned on, is this why 7-15 hour games seem so unreasonable to me?
if my AIP is supposed to be as low as you say, how many systems should i take?
is the super terminal a major priority once i get a large fleet and hacking progress?
how important is it to deep strike co-processors and data centers?
can i just take a small contingent of ships with assault transports across the galaxy solely devoted to tachyon sentinels?
oh, i almost forgot the whole reason i started this thread. how does the AI generate HUGE amounts of threat while my fleet is at home doing nothing?
so many questions and i find it extremely hard to prioritize tasks. stuck on diff 8... (been playing so much i almost hit CTRL+"comma" instead of CTRL+"V" to paste hehe)
Threat is the number of freed AI ships that are not currently guarding something. This number goes up as you fight in AI systems (destroying what they guard, for example), perform dep-strikes (New AI ships are created as threat), or a lot when a CPA (Cross Planet Attack) occurs.
You can lower threat by sending out your fleet to hunt down and destroy gatherings of AI ships. Threat clean-up is important, because AI ships are not stupid - they won't blindly suicide on your defenses. They usually wait until there are enough of them, or until you expose a weakness, before attacking.
Deciding when to deepstrike (to destroy a Data Center or Co-Processor) requires knowing how much threat you can handle, and how much your action will generate. Unfortunately, that's something you'll need to learn on your own, through trial and error. What many players will do is a repeating cycle of: 1) hunt down and destroy the threatfleet, 2) perform a deepstrike or wait for CPA, 3) hunt the threatfleet again, etc. This keeps the number of aggressive AI ships at a minimum, leaving you slightly safer. If you find it difficult to keep the current threat to a minimum, then deepstriking is usually not a good idea.
How many systems to capture is also hard to answer. The simplest answer is "As few as you can while still becoming strong enough to defeat the AI." Again, experience will help, but most people will try to keep AIP low until the final attack on the AI homeworlds. What 'low' means depends on difficultly level and map and play style, but as was suggested in a previous post, anything over 200 can become difficult to deal with.
So, then, "how many systems should I capture?" should be rephrased as "How high can I raise the AI Progress level by capturing systems?" If you play with Core Shield Generators (CSGs) then you need to first account for capturing enough systems to take down the shield networks. That's 4 A-network systems, and 1 each of B-, C-, D-, and E-network systems for 8 in total. 8 systems is 160 AIP minimum (Command Station + Warp Gate). In addition, you would be well advised to capture a system or two with Fabs, Core Turrets, Advanced Factories or Starship Constructors, or other things that make you stronger. Finally, deepstrikes only occur when you are more than 4 systems away from a non-AI controlled system. Capturing or destroying a system 5 or 6 hops away from your territory can greatly ease the pain of attacking distant targets (keeping threat down).
AIP will be lowered by destroying Data Centers and Coprocessors, or by using the SuperTerminal should one exist in your galaxy. Data centers reduce AIP by 20, 15, or 10 points each, depending on your difficulty level. Coprocessors reduce the net AIP by 60, 45, or 30 depending on difficulty, but they also raise the AIP floor by up to 20 points while doing so, and you don't get the bonus until all 4 are destroyed.
This means that in a galaxy with 6 data centers, a set of 4 coprocessors, and no superterminal, you can expect 180 points of AIP reduction on difficulty 7. Counting the 160 points of AIP your are required to take and the 10 points you start with, you'd have -10 AIP. Trying to keep the AIP below 200 means you could capture about 10 systems beyond those with CSGs.
Note that taking the systems with CSGs is usually a good thing. For example, the A-network CSGs always occur in systems with an ARS - giving you a new ship type for taking the system. B-network usually occur with an Adv Factory or Starship Constructor, and C-s occur with Fabs. So you can serve a double-purpose by capturing those systems.
Also remember that there are all sorts of other things that will raise AIP - Warp Gate raiding, destroying special AI structures, using missiles or Nukes, time passing... As these things occur, the number of systems you can safely capture will go down. It's a trade-off that you will need to keep in mind as you plan your campaign.
Finally, to reiterate, the largest source of threat will usually by the Cross Planet Attacks, which will occur every few hours and are announced up to 30 minutes beforehand. It is usually a good idea to stop offensive operations when a CPA announce appears, and focus on killing existing threat and preparing your defenses.
