"Time in erodes awareness of" is another way of saying that the longer you are in a particular situation - your home, your church, your car, your job - you grow less and less aware of the peculiarities of that situation. The scratch on the door. The funny noise of the brake pedal. The slightly torn window shade. The peculiar smell of the breakroom at work. You grow used to these things. They go unnoticed.
That's the danger of being a lifelong Christian. You might overlook something that is really more important than you think because you've heard it so often. It's like saying the Creed or the Lord's Prayer. It can be pretty easy to slip into autopilot as we speak words of profound spiritual depth and value.
