I've just came back from a wee 800 mile scoot round Scotland and this is what I found with my Front tyre
Avon Distanzia, about 18 months old 8K miles roughly it's all the way round the tyre on the RHS only and some of the cracks extend down into the sidewall, the tyre does have that old rubber sheen to it, but I've had tyres on other bikes being older and never had this, small surface cracks around the grip blocks yes but not this deep there about 1-2mm deep
I have just put 250 miles on a new Tourance EXP's and the release compound is still on the sidewall and in between tread blocks plus a few mm chicken strips (shiney shiny) your pic looks more like my old tyre.
Dave
I'm certainly no expert but that looks suspiciously like the belt showing through the rubber between th eblocks. If I'm right the blocks are effectively just stuck onto the belt material, (some kind of nylon?), and I wouldn't ride that at more than about 30mph directly back to the tyre centre.
Secondly, why would you fit EXP's when the original Tourance can be ridden all the way to the side wall, on the rear at least, gives much greater life and costs less than EXP's? On a circuit I produced some nice little beads of molten rubber along the edge of the tread on my 1150GS and was told to hang off the bike more before I rode off the tread
With smooth riding I've had 12,000 miles from a set of original Tourances and others have had more. Even riding harder you can expect 7-10,000 miles.