How much do you keep in your savings account?

I get paid monthly, I wonder how much is a good amount to keep in my savings for emergencies. I normally keep 4 weeks worth of pay but I hardly ever need to dip into that. I wonder whether I should only keep 2 weeks and invest the rest.

I have a decent share portfolio already, and I have properties, the amount in my savings accounts is only for liquidity purposes. I spend around 60% of my pay.

Thank you keen to hear your reasoning.