Salamandrine 

Maybe some suspicion is due, but i'd hesitate to blame them.

Cracks around the spoke holes are caused by too much spoke tension. An old rim that has been trued many times can develop these cracks. Spoke tension gets progressively less even as the wheel gets progressively more old and bent. Some spokes have to be tightened to keep the wheel true.

It can also happen because hamfisted modern mechanics use too much tension on a vintage wheel. 36h non aero rims did not use or need anything approaching typical tensions used today, and modern high tensions are likely to fracture the rim.

In this case I'd guess the former. For someone that rides 100/wk, I'd expect the rims to last maybe 3-4 years, depending on conditions. They are long past that now.