Same goes with races where the routes are ones you are familiar with. You would know where to conserve your speed, where the steep climbs are and where the descents will be, where the toilets are in case of emergencies, etc. and all thse factors that could help you in attaining a new PR.
But... sometimes you need a change in scenery, something that makes you wonder at the new sights and make you forget about training hard. These are for the easy days in your training or even the LSDs, where instead of focusing on time, you look around you instead and enjoy the sights.
That is why I enjoy joining races where I hardly run in, be it international races like New York (which I super love) to Berlin to Disneyworld Orlando. It can also be local races like Cebu, Baguio, Subic where I never run in as well! But it doesn't have to be races when running at new places.
When we went to Japan last year, I made it a point to run in most cities we visited: from Tokyo's Imperial Gardens, to Hiroshima's Peace Park to Kyoto's temple city, it made exploring the city that more special for me and at the same time, as I ran in certain parts of city, I would know which areas will be interesting for us to visit in. So that also help save time.
For Metro Manila, I ran on EDSA on Dec 31 where there were hardly any cars on the street and did a big loop, which took me to C-5 and back to Makati. It wasn't part of my regular route but decided I wanted a change in my route.
Yesterday, I ran from Tagaytay Midlands to Tagaytay Highlands, well "ran" in a very loose definition as walked most of the way due to the very steep and long inclines. It was tiring, it was horrible and my legs were tightening up the entire time. But it was also something I had never done before. And when we drove to Tagaytay Highlands to have lunch and passed by the same route, I was enjoying the scenery and how I survived that run. I will never look at it the same way again as I knew how hard it was to get to Point B from Point A and back again.
So it's good to do your routines and that should still be the core of your workouts. But don't be limited by it.
The world is one big road. Keep exploring it. Keep running it. Keep expanding your experiences! Be open to new surprises!