Your Permanent Resident Card is proof of your status in Canada but when the card expires it does not mean that your status has expired. The PR Card is the best proof of status in Canada, so you should apply for a new one the moment you are able.
If your card does expire, you will be unable to travel outside of Canada and you may experience issues proving your status, as many government agencies and private organizations will not accept a Record of Landing or Confirmation of Permanent Residence as proof of your status. Get your PR Card to avoid problems.
You will know if your status is in jeopardy or you have lost it because you will receive mail or email correspondence from IRCC regarding your status, triggered by an application for a PR Card, or by a criminal conviction. Make sure you meet the residency obligation before applying for a new PR Card.
How Do I Lose My Canadian PR Status?
The only way you can lose your status is through an investigation into your status (triggered either by not meeting the Residency Obligation but still applying for a new PR Car or a Travel Document, or by a criminal conviction) or by voluntary renunciation.