Personally, I'd say 1-3 years on a single character as a 'minimum' is inaccurate, though I don't think that's the point Dawn was trying to make.
Rather, they play those characters for a long time, and as a result, their characters are well known, and have more opportunity because they are established as 'reliable', and continue that route because of the time they put in. Which, is quite a lot, and they've played both evil and good with this. It's a lot harder to suddenly trust Gary Jameson, who's only been on Arelith for a week with planning and information- you simply don't know if they'll be there tomorrow or what direction their character will take.
Now being seen as reliable doesn't take a year, not in my experience. I've had characters who got their foot in the gate in the first week, others in the first month, and become people who have the ability to make changes or run things in relatively short period of time. Some of it is luck, some of it is because I only focus on one toon at a time and therefore am around more and 'seen' more, and usually have some loose idea of a goal in mind that I work towards consistently. But, one thing I'd advise against, is making a brand new character fresh off the boat who immediately comes in and wants a position of power to change everything. That almost never goes over well, for a variety of reasons. Start small, work your way up, if you put in the effort and have a bit of patience, it really doesn't take that long! And don't get discouraged when you get a 'No', ladders of success, whatever that might mean to you or your character, aren't a straight-shot upwards. Rome wasn't built in a day, after all.
As for the main point of this post, Good Vs. Evil when in Surface Settlements...
One thing to remember is the politics at play. Plenty of characters are of the mindset that what they do is for the Greater Good, even if they're committing evil acts. While the Alignment Chart is all well and good as it provides the majority of a character's intentions, it's also really more of a guideline since fitting any one toon completely into ONE of those little squares is extremely difficult- and this is where the term 'Lawful Stupid' is often used, though that might be personal opinion. People in general are complex, this is what makes them interesting.
How factions like the Cordorian Guard (since it was brought up) tend to go, is often ebb and flow between being more chill, more vigilant, more 'trigger-happy', or even more corrupt. The same is true for Andunor, Guldorand, Myon, just about anywhere. If you don't like the direction one place is going at that moment, it's absolutely okay to try somewhere else out for a bit and see if you like it better! That's the best part of RP, you can move around and experiment!
Playing an evil character can be challenging, as you can't outright BE evil in a Surface Settlement, you have to be sneaky, coy, and have a sense of secrecy. It's been done many times with flying colours of success and amazing stories, when they're allowed to play out. Meta-gaming, on the other hand, should be 100% reported. Even if you don't have proof yourself, the DMs absolutely can find out for you.
My recommendation to those struggling with it, would be to either try to play a political evil entity- by being conniving or even a liar and worming your way into high spots of office or a faction to commit your evil deeds behind a security wall, OR, growing your little evil circle of bad guys in a somewhat out-of-the-way location where they may just fester and plan until their targets don't even know what hit 'em until they're eeking out into their cities. But, as above, both take a bit of effort and patience, and that really is where the majority of those amazing stories we all hear about come from. The journey there, not the destination.
Something something real treasure, something something friendship along the way.