To set the record right:
P-plate is mandatory in the first year in other to warn others that
you are still a new and inexperienced driver. Therefore, if you
never put it on during this time, you will get caught and licence
revoked.
After first year, you can take down the P-plate, as it is assumed
you have acquired a year of driving experience. However, some
drivers who are still unsure about their driving can and should put
up the P-plate, as this is to warn others to be cautious of you.
Not a crime if you put it up after the first year is over.
Finally, P-plate dun mean lousy driver and non P-plate dun mean
good driver. Cheers! 
