The habeas corpus debate is a classic slippery slope argument. Make the standards too loose, and the floodgates of frivilous collateral attacks on convictions open. Make the standards too tight, and innocents rot forever in jail.
What room is there for middle ground?
What if it was possible to revisit the validity of a conviction say, once every seven years? The vast majority of sentences would never be eligible for review and most that we eligible for review would be eligible only once, limiting a flood gates effect (the de facto federal habeas corpus reality now). But, this would simplify cases by reducing the procedural complexity involved.