CS,
That is indeed the case. It's a rolling seven years too.
If you renew an IR within five years of expiry, I should allow about 2K to renew it.
If you go beyond the five years as I did, you need to pay another visit to CAAFU, training as required. I recon this will cost you between 6K and 16K depending on how it goes. Each test will cost areound 1200 pounds a shot (test fees 600, plus two hours a/c hire and approach fees)
HTH
PS