Camshafts: What effect does increased lift have on performance?

Syleng1 said

But you cannot increase lift and have the same duration. Mathematically impossible. The extra lift increases the duration or you have an awkwardly weird ramp rate.

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Ramp rates are wildly different for tons of cams, even just flat tappet cams, in the case of Mopar's(AMC & some older Olds) the large tappet diameter allows for crazy ramp rates, it's even more ridiculous for mushroom tappets. You can 100% have much higher lifts with the same seat-to-seat duration, the question is how much You want to push it, & do You want to do/spend the $$$$ what's needed to upgrade the valvetrain.
The amount of benefit depends on the heads & what range of operation You're talking about. Take stock SB X/J/U heads, they pretty much nose-over @.475" lift, some less than others. Increasing the lift still gets the valve open quicker & spends more time in the lift range where the heads are flowing more, even if it doesn't flow much or any more at the peak, as long as the head doesn't 'back-up' dramatically it's still a win.