One should have just one or two favorite routes ... or things get too complex.
On my route I have @ 300 + miles (or possibly 500 + miles including brachlines).
When I get tired of the mainline construction, I switch over to a branchline construction, on the same route.
Even the Horseshoe route from Huntingdon to Johnstown gets kinda boring, and seems to be just an up and over the mountain route, after thousands of hours working on it.
Fortunately this route has an unlimited number of branch lines to keep me sidetracked, and keep me refreshed.