If anything much of that money should be sitting in their TFSAs. Between them they have over $50K in contribution room available. 

Then when they need it to purchase a new home there are no tax consequences involved with the withdrawal. 

Long term retirement savings only should be directed to RRSPs. 

Here are some numbers on how many people actually make the payments due on the RRSP HBP. 

"CRA told us last Wednesday that almost one-half of HBP participants (47%) “paid less than the full required repayment amount in tax year 2011.” (2011 is the latest data available.)"

https://www.canadianmortgagetrends.com/canadian_mortgage_trends/2013/02/disappointing-new-stats-on-the-rrsp-home-buyers-plan.html

If you don't repay the loan, you lose the RRSP contribution room FOREVER!  That is the worst case scenario, even if you do repay the loan you lose up to 15 years of tax fee growth.  As enticing as it sounds the HBP isn't a good deal.