Eric, I can’t help with the age too much. Tough for me to tell. In general if you think it looks between “new” and a year or two, just say that.
As far as 4 layers… are you seeing 4 shingles at the drip edge? Could be 2 layers as well. A starter course and then the roof, 2 each x 2 layers = 4 shingles. If there were in fact 4 layers… this is definitely a problem. My area used to allow 3 layers, now it’s 2. Most professional roofers never did install the 3rd layer anyway, it was done when someone got some “help”.
The roof looks a bit wavy, like a roof over.There are some concerns that you may wish to mention with really wavy roofs as far as roof’s service life etc. Did you look between layers (if possible) to see if underlayment is between layers?
The spacing and staggering look OK, but it’s a bit hard to tell from an angle. Where the siding meets the shingles does not look OK IMO. Possible flashing issues and clearance to siding doesn’t look great either.
Posted a pic or 2 for ya.
