My understanding of valve clearance is the following -
You need a minimum clearance at operating temps so the valves seat completely. If they don't, you'll burn the valve and the seat plus lose compression. Valves are kept cool by transfering their heat through the valve seat and into the head. Also the clearance is reduced over time as the valve face and seat wear (valve pushes higher up into the head). If you're looking at a 16K interval and you start with a clearance less than the minimum, the wear might be enough to prevent the valve from seating and it will reduce the amount of time it can transfer heat to the head. Also you don't want the clearance too much as this will cause excessive wear, clatter etc. There is also the issue of valve timing. If the clearances are too tight, your valves are staying open too long, reducing low end response. Too loose and you don't get enough duration for top end performance. If one valve is out of whack, that cylinder will not perform as well as the others that are in spec.