Hey Flex,
Just email TC. Ask for someone in personal licensing and ask about maintaining a foreign IFR to "preserve" your written exams.
I'm sure you won't have to write the exams again if you just show that you have maintained an IFR somewhere else. You will just have to do the practical. I'm also sure they will tell you there is not a 5 year limit on it. Just email the people that regulate it instead of asking here and getting all sorts of different answers.
You can even periodically send a copy of your current foreign licence and a copy of your last ride to TC to add to your file to maintain the constant proof.