It is true that every site needs revenue in some form, or they won't last forever.
Even the most capable site manager cannot sustain a website alone without devoting income.
Newgrounds does have a means of profits, even if Ads are practically non-existent compared to other sites.
Still donating will certainly help. If people someday don't spend enough on shop items and support the occasion game and series here and there than donating may even be needed.
For now, this gives a lot to think about. Newgrounds can last, but for how long?