When I recreated the MABDR in Tyre to Travel, the total route contained 468 waypoints. When I dragged the route from Tyre over to my Garmin Nuvi 2455, the Trip Planner feature couldn't find it (although I could see the route in the Nuvi's GPX file when I looked at it on my computer). I ended up breaking the MABDR into segments; the largest segment contained 151 waypoints, and the Nuvi had no problem opening it. I didn't do any experiments to see just how many waypoints a Nuvi could read in a single segment, but I do know that 151 works.
Breaking a long ride into segments is easy on Tyre. Create the entire route, then to create the segments, open a new file for the new segment. In the new file, go to the upper left of the screen to the "Waypoints" drop down menu, and select "Add". You'll get two options: "manually" and "from file". Select "from file", and choose the file that contains your complete route. You'll get a menu that contains three choices to import: waypoints, route points or route tracks. I've always used "route points". When you click "Ok", you'll get a list of all the waypoints in the file you selected. Decide which ones you want to copy to create your new segment; you can hold the shift button down, and use your mouse to right click on the first and last point of the new segment, and the computer will highlight the first and last point and all the ones in between. Then click "Ok", and the segment you just copied will appear on the screen of your new file. Then just name the new file, something like "MABDR Segment 1". There may be other ways to do it, but that way has worked for me without fail.
"No matter where you go, there you are."