It certainly is easy if you know the stopping points in advance.

One approach would be to extend the route, a bit longer than you expect to ride.

One could start the subsequent days at earlier points.

Or you could break the route into shorter-than-a-day segments.

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The Garmin 800 sometimes had issues calculating "really long" routes. It also pooped-out recording at around 180 miles.

The route calculation was slow enough that, especially if you were near the end, it would not have been good to calculate a route most of which was behind you.

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With the Garmins, you can have it both ways (sort of!). The Garmins let you display a route that isn't being used for active navigation.

So, you could display the entire route but use shorter segments for active navigation.