I bought Infiltrator to increase my Galactic Readiness and counteract its "decay" since my Internet is too slow for Xbox Live. (I use the Internet at my brother's house from time to time to update my console and to play multiplayer as needed.) I loved the game and got three stars on every chapter, which apparently unlocks a war asset in addition to the intel I gained. I currently have 168 intel and am still playing for fun. Can I use my intel and war assets from ME:I in multiple ME3 campaigns? If not, should I spread it out? How does 168 intel convert into Galactic Readiness? What ME3 war assets do I get from perfect scores on each chapter in ME:I?
Intel is a one-time shot. Upload it once to raise your Galactic Readiness, which will decay over time. Four intels raise the Readiness by 1%, and the Readiness will decay 3%/day before leveling off at 50%.1 You should wait to upload until you're about to finish the game.
Galactic Readiness is the same (concurrent) across all games and apps tied to your EA Origin account (including multiple playthroughs). This said, you need an Internet connection to sync with the EA Origin account (both to upload intel from Infiltrator and to update your Readiness on ME3).