PI lawyers - how often are you paying for medical record summaries?

I'm helping my dad set up his solo practice in California. He went solo about 8 months and have been doing mostly car accident cases. He insists on doing all his own medical record review and it's now taking up a big portion of his time. He doesn't want to hire yet because his caseload still fluctuates. PI lawyers of this group, how often are you paying for medical record summaries? How do you know when it's time to hire additional staff?