You need to meet the RO - minimum 730 days provable physical presence in Canada in the 5 year period prior to PR Card renewal. If you have been a PR less than 5 years the RO window is from landing date to the 5th anniversary of your landing date. Processing times thereafter are determined by your application being routine or non routine. For the latter CIC will ask for more documents or call you for an interview. Most PR Card renewals that ahve problems are either the PR messing up their day count so apply with a buffer of days not exactly 730 or having weak evidence of physical presence e.g you were are unemployed and have lost your passport so no stamps evidencing travel and days spent in Canada nor any employment tax records indicating you were in Canada.
