You would be crazy to stay in the lounge for so long. Going to TLV, you will have access to the Swissport lounge. It's not worth more than an hour or two. I was in there at the weekend and it was quite loud [there was quite a party going on in the smoking lounge, and the lady in the seats behind me was video calling everyone in her contact list, it seemed] so it may not be as restful and relaxing an experience as your friend might like!

Go into Athens, have a nice lunch, see a bit of history, and return to "relax and enjoy" the lounge (to the extent that it is possible).

[And I am unsure about whether they will welcome you in 8 hours before departure...but I expect they would not be happy to see you so early. Whatever fee they charge Aegean is probably not designed to include all-day visitors!]