Adjusting the valves allows them to continue to close properly. Clearance between the round part of the cam and the valve stem will diminish over time, because the valves wear into the seat, allowing the stem to rise slightly. As this rising persists and the stem stays in contact with the cam 360 degrees, the valves never totally seat (close off). A valve that never closes completely loses compression through it and will also run hotter, because in the closed position against the seat, heat dissipates to the head. As the compression drops the result is a poor running engine, difficult to start, and eventually the valves can litterally burn up.

So...you did good by adjusting your valves. Your engine will thank you with continued good performance.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold