Yesterday I called into a tyre place because I thought I had a puncture and wanted to ask about my front tyres as they were looking a bit past it. When the car was on the ramp, the guy called me to have a look at the back ones. There was a fine line down between the tread. To me, it looked like it was where the tread meets the tyre. It wasn`t a crack as such but there was definitely a line there. He said that I needed new tyres because they were coming to the end of their life and the oil in the rubber wears away with time. The car is a 2011 car which I had as a pre-reg (can`t remember which time of year I bought it) so the tyres a indeed a few years old. Was he stringing me along?
Tyres do have a finite lifetime, independent of mileage. I change my caravan tyres every 6 or 7 years even though they are not worn out. There is a 4-digit code on the tyre wall which gives the year and month the tyre was made eg, 1411 indicates week 14 of 2011.
Your tyre rubber should not have deteriorated over four or five years. You must have had one MOT test so I'd go back to the people who did the test and ask them to look at your tyres as a favour - if they value your custom they'll do this for free.
of course it all depends on what mileage your doing,did you get new tyres if not take it to a few places to get them looked at (not one of the big name ones like kwik fit ,they just after tyre sales etc)
I work with vans that do a lot of miles and are on the road for up to 16 hours per day (returning to depot, not the same driver for 16 hours), if I have the smallest doubt about the condition of a tyre, I'd get it changed.