8 seasons with 15 episodes had 8 x 15 = <<8*15=120>>120 episodes
4 seasons with 20 episodes had 4 x 20 = <<4*20=80>>80 episodes
2 seasons with 12 episodes had 2 x 12 = <<2*12=24>>24 episodes
All together, there have been 120 + 80 + 24 = <<120+80+24=224>>224 episodes.
The average number of episodes a year is 224/14 = <<224/14=16>>16 episodes
#### 16