IT really is a choice made at the beginning of a campaign, as to how big or small it's going to be. THe campaigns tend not to grow too much over time if they start street level, as experience in Hero tends to make characters more versatile, and durable, rather than more powerful (in general). Experience points granted tend to be 2 and 3 points a session, and only the most disciplined player sits on them for a full 3 to six months of weekly play to buy another slot on their multi-power, or a new power. So in general, heroes will make slow moves away from the street level, towards full power. Also , GMs should remember that villains get experience points, also. THey can grow as well, though not quite at the rate the heroes would.