I finally have my "black Friday 2021 flights" coming up. Booked Hannover, then in February/March or so Aegean didn't exactly abandon the route but rather moved the twice a week service by 1,5 and 2,5 days respectively. They didn't even need to get an excuse from me to re-book us to Düsseldorf. In fact, because the phone agent back then didn't actually complete the process of re-issuing the ticket (the new routing was saved in my booking, however I couldn't make any changes or even reserve seats and I never got the email I was supposed to get with the new ticket number), I was able to change the dates again to slightly better adjust them to what suited me best just 1-2 weeks ago without paying anything (keep in mind that fares for these dates are now extremely high and I expect the flight to be nearly full). I could have even changed the airport again if I wanted ​​​​​​.
Anyway they ended up messing up our seats for the outbound flight. I tried to apply the "book the row with 2+2 infants" trick where 8D-F appeared completely empty, only to notice on check-in that one of us was moved to row 9 left, because now the one seat of row 8 we didn't book was suddenly occupied (so not enough masks for 3+2). I ended up booking us C and D in the same row for this flight and then re-checked the return leg and it's still where I'd left it (same row/side). Let's see what happens with that (because if it also ends up also getting changed I'm going to let them know how frustrating this is ... I mean the, pretty much advertise how they would even make sure families booked in light fares get seated together and here they are changing existing comfort flex reserved seats​​​​​​).