I check the thread depth, may markers naman sa tyres.

If mejo makapal pa, i check the "lutong-ness" of the rubber based a peels and cracks.

If marami ng cracks, then my tyres are due for replacement.

The mfg date is not that important to me, i check it last if all three criterias above are met. If makapal pa pero 7 years na, palit na.