1998 civic's tapit's clearences can be adjusted.
Cultus has hydraulic tapits they dont need manual adjustments under normal tuning conditions.
Tapits setting directly effects the engine's behaviour. More clearence means more noise n lesser peak power.
A tighter cleance would result in rough idle n low rpm response with a bit better topend power(if the setting permits.
There is no rule about when to get them adjusted. it depends on the need of the tune of the engine. A car whcih CNG generally needs more freauent adjustments.