As the more knowledgeable haven’t replied I will have a go - but you would do as well to check with the CAA or wait till someone else is along.
I think your friends are thinking of the rules pre 2002 - after 5 years it was a CAA log book examination and they determined the retraining, after 10 years some of the exams also had to be retaken.
Since 2002 it is down to your friendly CFI to determine what retraining is needed. You will still need to get your log book signed off by the CAA and of course they will charge a fee for the privilege. Maybe it is the fee your friends have in mind because after three, four or five years you will need some retraining one suspects in any event.
Good luck.