How much do I need to run to maintain aerobic fitness?

I run a fair bit but am struggling to keep up with my routine cause of work commitments. I currently run 3/4 times a week. Each time I run, I do 30 minutes at an average pace of 7 minute miles. My heart rate during the run usually sits between 160-175 for the entire 30 minutes.

How many times do you think I would need to run to maintain this fitness level? Also, would this be considered an intense cardio workout? I am an 18 year old male.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).