Doing only ?-4 and grabbing any SG that comes up, I'm at 446 papers now.
That means, that I'll probably reach 2,000 papers before phase 2 starts. ?-8 generally rewards more tokens, on top of that, phase 2 sometimes spawns special raidbosses or gardens.

So, I'm not really worried about reaching 4,000, I'll get there during the next phase. And there's no point to farming beyond that these types of events, unlike the last event we had. There won't be any more additions to the rewards list, no purchasables, nothing.
But, as has been pointed out repeatedly, to get the fully unlocked girl, you only need 2,000 papers. More papers is just for the "extra" gold, seeds and ampys. Heck, I might even skip a day to get some purple dragons, since my stock ran out after evolving both Tachibana and Strawberry Candle this week.