Most of the time I only ever got up to 500 days or so (at the first play throughs). I almost always used the Battle Sizer mod and TweakMB when I played "Vanilla" SP. The longest (my 2nd or 3rd time starting a new game) I ended up helping the Nords take over most of Calradia (we wiped out the Swadian faction entirely, and had most of the Vaegir territory). I was a "faction man" that whole time early on, since it was hard going at it alone (when I was new). After that I started working towards my own goals, to gain territory, acquire wealth and start a faction.
I usually always start in Nord territory (since they have best infantry, I can get the free "Strange" equipment from Tihr and Rivacheg, and can start fighting Sea Raiders for best loot early on). Then I recruit Vaegir's to make into archers. And then I get Swadian's for my mounted troops. I would usually always join Nords because they have the best troops for storming a castle (IMO). I would work on getting my army upgraded (both regular troops to higher troop levels, and also getting my followers to higher levels and better equipment). I'd raid villages of enemy factions whenever possible (and cross my fingers I get something expensive like Linen to sell). At the same time I'd try and do as many quests for friendly Lords and the King as possible (so I am in better shape to get nominated for Lord of whatever Castle that I'm setting myself to attack and take). I would do a lot of Tournaments as well, to make some decent money (I'd increase the money you can bet using TweakMB).
At the same time trying to recruit more companions. I'd use this guide so I don't get people who dislike each other
http://strategywiki.org/wiki/Mount%26Blade/Companion_Builds :
After I besieged and physically captured a castle I'd wait to see if the faction made me lord of it (if so, then I would stay in the faction, if not I'd leave and keep the castle). Then I'd start stock piling my highest tier troops in the castle and try to get another set of troops to as high as tier as possible in my standing army (so I have an army of highest troop trees in my castle and also on me). Then I'd try to take over a city if possible (usually would try to attack either a strategically important city (near my castle or else centrally located on the map for highest trade bonuses), or else a weak city that was recently taken over by another faction (so low troop numbers). After taking it, the faction I was with would normally not give me that city, so I'd end up leaving at that point. And then try to stock pile a garrison of troops in that city, and start working on my supply of troops in my standing army.
This "early" in the game you don't usually last too long as your own faction (you're an easy target for all factions), so I'd usually try to join another faction and then I'd be recognized as "Lord" of my City and Castle. The Khergits were usually a good faction to join, because I hated having them attack me on open field battles, but I usually wasn't too picky about who I joined (would maybe join a faction based on who they were at peace/truce/war with and how it affected the proximity of my castle and city).
This is where my games usually trickled off or ended outright. I suppose if I kept playing I'd try to grow my empire, but most importantly I'd be trying to make friendly with other Lords in Calradia so they'd be more likely to join my "Faction" when I create one. Other times I would take up the cause of a pretender, but I didn't see much difference between that and being a King of a faction myself. So I usually chose to become my own faction at some point.
