Totally depends on the game, the geometry and number of shots required, rules, included whether multiballs can be used to take risk out of some deadly shots.
The difficulty of getting there on Metallica was a coding misjudgment. Lowering the shots required is the only way to open up the game and make it more fun. Otherwise you're forced to bang away on the captive ball FOREVER. Too random on the rebounds, which sucks a lot of skill out of surviving the journey.