Straight to the point: give more experience for players having more time in-game; for example, Think of a EggWars game, Team A vs. Team B. Team A and Team B have been battling it out for a while. It's an hour now and Team A wins the game. They are awarded 250 Experience and 50 points.
What I'm saying is that award player more experience and points for the longer they play a game. For games with time-limit it won't be a problem, for EggWars the rewards aren't always fair. For a game that lasted for maybe 1-2 hours, that amount of experience isn't enough. (This is very common in TeaParty)
Solution:
Give 750 Experience and 150 points for games over an hour. (Within that hour I could've won 3+ games.)
It could even award based on the minute milestones (30+ minutes = 500, 60+ = 750, 90+ = 1000 etc.)