If I remember right, back then, the events had an infinite quest list. So those players with multiple bases didn't necessarily spend money for the bases. After you had the 9 artefacts, you got a new set of bases, ad infinitum. Someone motivated enough could have spent a lot of time boosts to rush through a second set of quests.
I wasn't there at the time, but I definitely gamed the system over one of the next events: didn't spend any event currency, and then splurged it all on the day the prize was the wishing well. On my live cities, I still have wishing wells in storage, ready to go.
(I didn't do the same trick on the next event, which I should have... little did I know that Innogames was going to remove the wishing wells from the prize list, permanently).
That said, fire phoenix definitely needs feeding, so you're limited to the number of pet foods you can craft...
but people with several phoenices have been playing a long time... they can very well be in the end game, with a time warp at insane level, which means that they can probably feed all their fire phoenices once... do all their rounds, ascend through the full spire with time boosts, and be done for the week.
there's one point where you have to leave people a bit of leeway for optimization, and also reward people who have been at this for long, in my opinion.