How long does it take to finish a game on the 1 day setting?
On a 1 day setting, you can finish a small or large map within a couple weeks, but you might have a tough time finding opponents willing to do 1 day turns. The difference between small and large in this case is how much time you'll be spending on your turn each day. For smalls, it never takes more than 15-20 minutes (depending on how much time you take to plan your strategy, rewind, etc). However, for the largest maps, it can take up to an hour per turn in the late game.
That is the reason most people prefer to have 3 day limits, and play more games, so they have more flexibility. Rather than having one or two games that might take up a big chunk of your free time each day, you have a few more but the option to break them up into 3 day chunks if you get behind.
The best way to play a game quick is to talk to your opponent as you play, using some kind of messenger.
I heard that an xpac/new version is out. Is this PC only? If it is i guess i need to get it for one of my PC platforms since i cant wait 6 months to a year for the Mac release.
There are two additions to the Massive Assault series that you may be talking about:
1) Massive Assault Network(MAN) is the original game optimized for multiplayer performance. It has features to make it easier to help your multiplayer game experience (in-game chat for one), and comes with several more maps (including the newly released Trinity). It is currently available by subscription only for the PC. This version doesn't have much support for single player, however. http://www.massiveassaultnetwork.com
2) Massive Assault: Phantom Renniasanse. This is the much anticipated sequal to Massive Assault that should be coming out early next year. It will dramatically improve the single player with upgradable generals and additional game types, it will add many new units to each side, making each unique, and will add more map features such as destroyable bridges. I don't know about the plans for a Mac release, but I'm sure as you said it won't come for 6 months after that if they even do the port. See more at http://www.phantomrenaissance.com