I have a few running routes, but my long runs are all either alongside the canal (between Hemel Hempstead and Watford, or between Hemel Hempstead and Berkhamsted) or on the footpaths and bridleways of Ashridge. I run these routes repeatedly but never get bored, instead it seems that the more I run them the more I enjoy them.
It has something to do with a sense of ownership. By continually imprinting these paths with my footprints I feel that I own them.
Reason No. 5 for running: You can mark out your own territory.