The most important thing to remember when making your own training regime, particularly when it comes to cardiovascular training, is to keep progressing.
I’ve worked with people who have run the same 5km course three-times per week for five years, without making any noticeable improvement over that time.
Think of all the hours of training that went into that routine - all it needed was a little bit of optimisation and that same training effort could have yielded more substantial gains.
Of course, if someone runs the same loop and it keeps them active and maintains their body composition, it’s not necessarily a bad outcome.
However, if there is an opportunity to get a greater return on your fitness investment, I would always recommend looking into it.