I work for a mortgage insurer and we constantly track and analyze default rates by just about every metric you could think of and we spend a lot of time analyzing the life cycle of mortgage loans and default rates and know exactly when the default rates are likely to peak over the loan cycle as we receive claims for defaulted loans that we insure and we needed to appropriately model reserves that we need to hold against against future expected losses and properly price our insurance premiums. BTW, I just spoke to one of my modelers and I was slightly off with my 3-6 years peak for defaults on 30 year mortgages, he thinks the peak is in years 2 - 5 based on the data he has analyzed (which is a a heck of a lot of data)
BTW, there is loads of loan performance data that can be downloaded free from both GSE's and Ginnie Mae...anyone with the skill and inclination can do an analysis of this data...although it takes quite a powerful computer and an ability to deal with SAS as the amount of data in the datasets is just too large for typical spreadsheet programs like Excel to handle.