Tires developed some cracking, would you replace them?
 

I recently had my Audi serviced after extended non-use (about a year), had a few mechanics look at it, ended up changing fluids and brakes. Neither mechanic mentioned anything about tires, which I've bought over 4 years ago (they're Michelin Pilot Sport PS2 A/S with 50k expected life), put about 20k on them. Tires seemed fine to me too, and I passed safety inspection without any issues 2 days ago.

However, I'm letting a friend borrow the car for a couple months and she's concerned. One of her other mechanic friends is telling her that the tires are in bad condition and could get a blowout. I asked her to take a few photos to get a second opinion, here they are. I wanted to know what you guys think.