According to the CIC website the current wait time is 39 days. I'm not sure how accurate that is as I have seen some posts of people saying it took longer. Maybe they have caught up and are processing within 39 days now. I'm not sure.
http://www.cic.gc.ca/english/information/times/index.asp
It may be important for you to stay depending on whether or not you are coming from a country that is visa exempt and what your method of travel will be. If you are from a non-visa exempt country you only have the visa valid for your landing. If you leave the country without your PR card you will have to apply for and get a Permanent Resident Travel Document (PRTD) in order to enter back into Canada. Also, even if you are from a visa-exempt country (such as the USA) you will need a PRTD if you plan to return to Canada by commercial means (airplane, boat, train or bus). If you were driving from the US to Canada in your own personal vehicle, you could cross back into Canada without the need of a PRTD.
http://www.cic.gc.ca/english/information/travel-document/index.asp
There is no minimum amount of time you stay after you land. Many people turn right around and head right back out of the country. Just keep in mind that you may need a PRTD to return, depending on your circumstances. Also, you need to keep in mind that in order to retain your newly acquired permanent resident status you will need to be in Canada for a minimum amount of time.
"When you are a permanent resident, you can live outside of Canada, but must live in Canada for at least two years in a five-year period. If you live outside of Canada for longer, you may lose your permanent resident status."
"Minimum residency obligations
You must meet the residency obligation to obtain a Permanent Resident Card.
If you have been a permanent resident for five (5) years or more
•you must have been physically present in Canada for a minimum of 730 days within the past five (5) years.
If you have been a permanent resident for less than five (5) years
•you must show that you will be able to meet the minimum of 730 days of physical presence in Canada within five (5) years of the date you became a permanent resident. "
For more info on that see here:
http://www.cic.gc.ca/english/newcomers/about-pr.asp