@Richard-18 Maybe 500 would be reasonable? The underlying theme is multi-day trips. To plan those I often make a separate overview route covering the entire trip, just to get a feel for distances and time, etc -- and this is where I would run up to the 200 limit. The choice to recalculate the entire route on every click gets very tedious too, though, in this scenario, see below.
The current web planner is excellent for planning (a) single day routes, (b) on asphalt. You can of course put a bunch of day-trips in a folder and if you don't mind the work (add route -> add route -> add route...) show them at the same time, but that's about as far as MRA goes in supporting multi-day trips.
My ideal for a successor would be a planner that would support multiple segments that can be linked into a trip. With an overview of the entire trip (with insight into distances and times per segment), and with the possibility to drill down and edit into the individual segments. And flexible export and import options, eg, map to individual GPX files, to GPX tracks or GPX segments.
While we're at it: maybe allow mixing in offroad segments, so I can find a home for my TET and ACT tracks and bind them into my trips.
Side note: currently every route gets fully recomputed whenever you open it or edit it. I think the scalability of MRA would be much improved if they would cache route computations (routes are viewed much more often than edited) and don't open an entire trip in edit mode. In terms of resources, it would become much "cheaper" to work with multiple segments and >5.000 km trips. (And to show an entire folder of routes on the map, so I can see "where I and others have been".)
Well apologies for a lot of text in response to your simple question. Hope this helps. 
Cheers, -Peter