Just get started
Nothing is constant in the market: Your personas will change over time.
The key is to start putting personas to work in your product now, knowing that you'll have another group to address tomorrow.
As you assess interview findings, the majority groups will surface. There's always more nuance to be discovered, but don't let "paralysis by analysis" slow you down. Start working with the ones you know now and keep evaluating the other groups for future reference.
You can’t design for everyone
Assuming you follow an iterative approach to the product, then each "release" should focus on one or two personas at most. If the top three personas are defined, then you're ready to get started!
It's tempting to solve for everyone every time (especially for Sales ;-).
That will end one of two ways:
- Each story gets inadequate attention and no solution is really ready for release.
- Each story is well-developed and solves for everyone's needs.
12–18 months from now.
And your personas are all out of date.
Don't try to do all the things. You need to focus on one or two personas for each release or iteration. If you include multiple personas in an iteration, it should revolve around needs overlap not your design to make them all happy.
Ideal is pretend
For the record, this is a myth:
a number of 3 personas is ideal
Ideal for what? For the designer who doesn't want to think about more than three?
For a narrowly focused product with a small market, you may only have a few.
For a broader, mass-appeal product you may have a dozen or more.
When deciding if you have the right number, consider these points:
- A persona is a relevant, real-world type of person addressed by the product.
- Each persona has unique needs and expectations.
- Because of #2, existing or planned features serve each persona in a unique way.
One disclaimer on points 2 & 3: Overlapping concerns are legal, but it's the sum of the parts that makes a persona unique.