We will have no checked bags.
Will your bag comply with the 8kg limit Aegean has? ( and the dimensional limits?)
Looking at "spring" I see a 1055 AM departure, not 1105; I know it is just 10 minutes but it could be meaningful.
Your inbound flight can be up to 15 minutes late and still be considered 'on time' in airline statistical records. Your inbound flight could arrive 'on time' and leave you just 75 minutes , not 100 minutes, to make the change.
No idea where you are coming from but looking at the options for MXP-ATH, I think I would look at some other way to get from home to ATH. From what I can find you have a 'everything needs to work perfectly' to make a (scheduled) 90 minute transfer, or waiting til almost 7PM for the next Aegean flight.
The flex ticket gets you a no fee change, but if the later flight is already full.......
Good luck and happy travels
( not the kind of stress I would choose)