First bottle-conditioned yeast harvest question

OK, I'm a new brewer trying my hand at harvesting yeast from some Bell's Two Hearted I picked up from my local beer store.

I've had three bottles worth of yeast in a 500mL starter since last night but don't have immediate plans to brew a clone or other beer this would be appropriate for.

Should I wait for this starter to finish and fridge in a mason jar until I'm ready to use(and then re-starter of course) or should I step this starter up before storage and if so how much?

thanks for the help

You can let it finish then put in the fridge.