520 plus very slow calculating routes...

soooo long

Define what that means for you?

But yeah, some routes, especially longer ones, may take up to 5 minutes to calculate.

In excess of ten minutes for 20-25 k routes.

I have the 520 Plus and have the same issue. I plan a route in Connect and add waypoints at every turn yet I set off on a quick 12km ride to a mates house and i was halfway there before it had finished calculating and started displaying navigation.

I get it if i had just put in the destination and was asking the device to calculate the route but i entered a very detail route and still it is slow.

IKR. One would say that if you plan the route in the Connect, have the Connect calculate the route and then sync it to Edge, then the Edge unit should just follow it without a need to do some excessive calculations or other whatnots.

But to answer the original question - I've never had a problem with such long duration calculations even on 100km and longer routes. Tho it has proven for me that deleting of all historical trips has made the unit faster.

4977711 said:

and add waypoints at every turn

This won't making routing any faster. The track already has lots of points, either near or at the waypoint you are adding.

Adding waypoints at turns will tend to make the routing worse if you happen to plan the route using a map that is different than the map installed in the device.

It's fairly common that roads on different maps are not in exactly the same places.

So, if you place a point at an intersection on on map, it might be off the road on the other.

That can cause turn instructions that are not what you are expecting.

The routing doesn't have issues when the track is a bit misplaced as long as the displacement is smooth (not at turns, for example).

Bedasek said:

One would say that if you plan the route in the Connect, have the Connect calculate the route and then sync it to Edge, then the Edge unit should just follow it without a need to do some excessive calculations or other whatnots.

The routing was originally intended to create turn instructions for recorded rides.

People figured out that you could plan routes by creating a fake ride record.

That works so well that it's the usual way routes are used.

So, while Garmin could produce the turn instructions on the website (it's what Wahoo does), they don't and are not likely to do so anytime soon.

Being able to calculate routes on the device is an advantage over only being able to do it on a website.

Bedasek said:

Tho it has proven for me that deleting of all historical trips has made the unit faster.

The devices are not intended to be a place to archive all your rides.

There's actually a limit to the number of courses (100) and activities (200?) that can be stored. Going beyond these limits causes confusing issues. 

The 520+ is kind of an odd device. I'm not sure if it was as good as it needed to be for navigation. That's one reason there's the 530.

At this point, I wouldn't recommend it (or the 820) for navigation.