Speaking purely theory and in general terms. Additional duration degrades lower rpm power including idle quality. It also increases upper rpm power. I may increase engine rpm capability before valve float. The added rpm capability may require stronger rods, pistons, bearings, and even cranks. It often is best done in conjunction with lower final drive gears. The increased higher rpm power may also require more fuel. The lower rpm power loss is sometime partually made up with additional ignition timing at lower rpm, but may need slightly reduced ignition timing at high rpm.
Cam timing measurement is not really a very precise way of measuring a cams potential. You can often tell more about the cams charistics from the cam grinder's literature than just trying to read the specs. One of the variables that is often hard to define is where does the valve start to open. There are two main ways of expressing cam duration. Advertised duration provides a larger number but is the hardest to pinpoint. Duration at .050" of lift is how most racing cams are speced but it provides a lower number. Another variable is how steep the cam ramps are. Steeper ramps (fatter lobes) provide more breathing than shallow ramps. The steepness of the ramps is limited more by metalergy than anything else. If the ramps are too steep, the pressure between the cam and the cam follower will cause rapid wear and cam failure.
So the answer to your question is that it depends on more than just the additional 10 degrees of duration. In very genral terms, 10 degrees of additional duration will only slightly decrease low end power with a reasonably decent increase in upper end power. It would probably not require stronger engine parts (although it would be beneficial). It would probably work well with the present rpm limiter (although it would probably really enjoy a slightly higher red line if the rods are strong enough). It would be wise to optimise performance with a custom chip dialed in with the use of a dyno.
Sorry about the brain dump. I do that sometimes when a topic triggers it.
