I am leaving mine till the middle of next month because I tend to cut things fine. It would essentially give me about 2 months or so for it to be processed. Others would definitely recommend doing it in advance. I applied for an extension on my PGWP last year, but that was a paper application, and so it took 4 months to receive my permit. An online application such as a Bridge, is usually faster and they cross check to determine your PR application as well. Honestly, at the end of the day, it's up to you on how you would like to proceed. I got worried earlier this month and put the application together. I just haven't submitted it yet because I am giving myself a couple of more weeks to find out what is going on (I am due to receive my GCMS notes in 2 weeks). Cheers.