Switching from REPAYE TO PAYE

Lets assume I'm switching from REPAYE to PAYE after X amount of years. Is the total amount of all those interest subsidies I have been taking advantage of going to be tacked back onto my loan balance or does the non-subsidized interest rates just start accruing from the point that I switch? Basically my question is what is stopping me from staying in REPAYE for 19.9 years and switching to PAYE right before the 20 year mark to get my graduate school loans forgiven 5 years early while still... Switching from REPAYE TO PAYE
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums