Doesn't happen as often, unless it's a small map.. Resets typically get hampered by a few things.
1)Overall the sides are normally fairly even, except in off peak times. So the maps tend to turn into stale mates or two countries gang on the third. So the end result, there are never enough bases captured, before the other teams gets a grip and fights back.
2)Typically when one country is on a roll and looks like a reset is close.. That usually means one of the other teams has been beaten down and lacks the momentum to recover. (There is always one country ganged by two)
That lack of momentum tends to cause the players on that team, to go fight in another arena or log off. That has the adverse effect on the team that's on the roll, because their ENY gets driven through the roof, (typically 15-29 when close to a reset). The high ENY ends up causing a stalemate and tends to allow one of the other two teams the chance to get bases back.
Team that's on the roll gets ticked off at sky high ENY and being only 2 bases away from reset and logs off. Their momentum is soon lost and one of the other team's momentum takes over.
End result, you are lucky to see any resets other than late at night by tool sheders, or on the weekends.