@
carefuldriver
As said, your licence is valid until your 70th birthday and then it is a self declaration to renew and then every 3 years thereafter.
Then photo licence element is renewable every 10 years (you are supposed to get a reminder but this seems to be hit and miss) but whilst it remains a separate offence of failing to renew your photocard, your actual licence still remains valid until aged 70.
At aged 70, if you have and wish to retain your D1 licence (minibuses) then you have to opt in and go through a full medical, and before you say that you do not have one, it is currently under discussion that new drivers will be able to get their D1 entitlement if they complete a MiDAS course which will be a much cheaper option then the £1500+ some schools are currently charging, so quite new and young drivers may well get the D1 entitlement.
(I should add that drivers who passed their test prior to January 1997 got their D1 entitlement automatically)
There is no requirement to take any retests, unless it was ordered by a court as a result of a disqualification or conviction or in some cases as a result of a medical condition or restriction. (The idea of compulsory retests was kicked out by the previous Labour government because it was deemed as a vote loser... See my post on this)
So... I don't know why retests are even mentioned.