I always did ~5 months early and a couple of times it came close to expiration before I had the new one in hand.
You only get the infinite grace period IFF the PD enters your data BEFORE your expiration. I know of at least one person who applied before his birthday but the PD just piled them up and didn't process them until after expiration. He was SOL and only had the 90 day grace period but couldn't buy/sell anything.
Thanks I am going to call tomorrow and check, I am approx 6 months out from expiry and would rather just have it in if possible