Ah, the magic question!
A 60–90-second PowToon is about the right length, long enough to tell a story and not long enough for people to get bored and forget your message. If they begin to lose focus, all your hard work starts to be wasted!
I once created an entire "microcourse" on a coaching technique that lasted 4 minutes, but that is probably about the limit in terms of time.
So, typically, a PowToon will be between 60 and 90 seconds long with around 230 words in the voiceover. This can be pro-rata (so, a 30-second PowToon would have around 80 words or so).
Here are 230 words; it is not a lot to get your message ...