Even if you don't stay in the top 25%, the extra days means more people submitting more data, which means the community goal could achieve its top tier, increasing the payouts, offsetting your not being in the top 25%. If you wanted top25 for the "glory"
ahem then that might not help, but materially it might not make much difference
(As you already know) everything you get from the community goal can be obtained by other methods and without grinding, so I don't think it's a good idea to grind for a CG payout; it sucks to wake up and realise that the game brings you no joy any more, you've burned yourself out on it.

(Fortunately there are plenty of other games to play until the itch returns

)
But I guess sometimes you just want the glory of being in the top25%
I did some exobio while I was out collecting planet data. That's already paid more than the top community goal payout could ever be, and I don't need the credits anyway, but breaking up the activities between FSS planet discovery and surface exploration of landables I found that had lots of bio signatures, it made for a better expedition. Especially because it meant that when using the FSS I wasn't just chugging along to accumulate planet scans, I was searching for a good place to do exobio. I think searching in addition to collecting made a nice difference.