You can renew at any time. Even if it's expired for like 2 years or even 20 years. As long as you are meeting the Residence Obligations (730 days in Canada in the past, rolling 5 years time), it doesn't really matter when you apply for a new one. PR card is only used for travelling outside of Canada and is not needed when you are here in Canada.
Again, your PR card expiry does not mean your PR status is expiring. They are not related. In my opinion, unless you need to travel, no need to renew. And you have passed your test! Which means oath invitation can come at any time.
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Advices from me are from my own experience and observations based on this forum.
You should never take them as legal advice for your immigration / application problems. Every situation is unique, please contact IRCC if you encounter specific problems.