Cracked Dizzy Cap / Cover - Worth replacing?

[Zilli]

how does a dizzy cover develop a crack?

[VTECMACHINE]

Mate, if I knew I would tell you. I guess it's because I have engine mount inserts, and therefore get more vibrations etc throughout the whole car. After revving etc, and backing of at 8000rpm, eventually it will crack the plastic casing.

Apart from that... i'd have NFI.