If you set the jets too sensitive the coils 23 800 of the old sys11 will get hot and burn or burn the driver transistors ,, the heat made by the transformer lamps and other coils between the bottom of the cabinet and playfield is not very good removed but this an extreme condition as machine works in an arcade environment 10 - 12 hours daily as is designed to work. WPC jets coils and late 88 s - 90 s sys 11 are lower power and more reliable at heat stress.
Probably if you play at home only one hour in a moderate climate environment old sys 11 coils will last at the edge !