as i read....
you have 4 discs...
1 Valk and 1 Leopard @ 168 +/-
1 Valk and 1 Leopard @ 150 +/-
throwing these two are similar but very different skill sets just the same. expecting to get similar results with 2 identical throws wont be productive.
if it were me, i'd ditch the 150g discs and take the 168's to the field and see if (after a few throws) you get the accuracy you seek. The yo-yo in weights is probably really messing you up. (the 150's, however, are a great way to practice form and eliminate OAT issues.)
FYI - with no wind, if throw flat your discs will do the following (if not beat-in to death)
Valk - If 300' is your max, throw at 80% power and aim AT something this is a placement disc. If throw flat, it should have a slight turnover and gentle fade (gentle 'S'). - I'd expect 275'(ish) it has the potential to point-shoot-park....(absolute precision)
if it's new it will fly straighter and get maybe 250'(ish)+/-
Leopard - If 300' is your max, throw at 60% and try for a very smooth consistent release; throw AT something as this is a placement disc. (Do not overpower this disc or it will flip). When thrown flat, it will turnover and drift before it fades. i'd expect 230-240'(ish)? this disc has the potential to point-shoot and park (in the general area). (aka "finesse")
if it's beaten in, it will flip and turnover for a long time.
once you can get the disc to perform as above, then you've mastered them enough to determine their true lengths and how they can help you. If properly beaten in, and thrown properly, discs will fly exactly (very similar) to the flight chart posted by innova.
For me, i throw a Tbird (300'), Roc (250') and a Rhyno (200'); course distance. I wouldnt expect (for me) that i would use Valk in ranges much past 315' and i wouldnt use a leopard in ranges past 250' (ish)??? <- I dont use a leopard or valk anymore so these are my guestimates. ????
*I'd probably use a Valk as a 275-300' laser precision disc and (probably) not worry about killing its accuracy in the longer ranges. But @ 275-300' i would know that if i had a line, the disc would be parked.
* i write this as i am not 100% certain, still, that your discs dont need to be replaced. and, you might have an incorrect perception of how far a disc should go or it's range.