Honestly for probably 90% of respondents 60 seconds is probably all it should take to approve or decline a mortgage.  For the most part it is a pretty simple bit of looking up your credit rating, outstanding debt, assets and income then a handful of calculations.

Of course if you read the fine print you'll see something like the following:

"[Mortgage prequalifying tool]  gives you an estimate of the amount of mortgage you may qualify for with us based on the accuracy and completeness of the information provided by you, is for illustrative and general information purposes only and is not intended to provide specific financial or other advice."

(Source: RBC's 60-second pre-approval page).