Limit on number of waypoints/guide points in either Basecamp or GPSmap 64ST

Well, not sure about the 64 but in most Garmin handhelds routes are limited to 250 points, so if you had 1200 points you were doing well 

No limit in BaseCamp, or if there is I've never reached it.

The limit is device dependent.  There will be one limit for Direct Route and another for all other profiles.  Typically it is 250 points for a Direct Route and 50 points for all others.  The number of points refers to the actual number of points listed under the route Properties tab - NOT the number of points listed in the summary section under the route Properties tab.

Setting the routing profile to Direct on the tool bar before converting a track to a route will allow the option to set the number of points.  You can change the routing profile after the conversion.

On some of the pages the set-up can be changed to see bigger numbers in the data fields, but this also limits the number of data fields.  For example, on the Map page you can click on the Menu > Setup Map and choose 1 Large data field which can be set to whatever you like.  I think there is also a custom setting that allows 1 setup during navigation and another when not navigation.

The Oregon and Montana handhelds have bigger screens, but I do not know if the numbers are larger or whether more than one large data field is possible.

Thanks. It seems that the first Route I created had 814 points shown on the More info line. The actual route on the devidce stopped about where the 800 points would be roughly 250. (it was about 1200 out of 3800)

The second time I did it with your Direct Route idea, it shows all 3800 points.

I think I need some software to "optimize" or "compress" the GPX track before I make it into a route so it won't have so many points. Many of them are just "still going along the route" so could be easily optimized away.

www.gpsbabel.org/.../filter_simplify.html

I have checked the Garmin site for documents and specs for my GPSmap 64ST, trying to find an official source that lists the limit. The "User manual" specification section doesn't have any reference to a limit.

Any info on how I can find out? I've got a gpsbabel shell command that seems to work, but there is no way to know if it worked to a real limit without going back out and doing the 125 mile ride again.

I finally figured out the right sequence of parameters to make it work in the shell. Never could figure out what it wanted in the GUI version. This worked, in that it made the file have only 250 points in the track:

gpsbabel -r -i gpx -f infoo.gpx  -x simplify,count=250 -o gpx -F simplerfoo.gpx

Out of interest which BaseCamp version are you using? When I convert a track to a route I'm asked how many points should be in the route.

For your device, the limitations can be found here https://support.garmin.com/en-US/?faq=rFMnK0E1GOAC7SG3rGhV0A

Garmin stopped putting this information in the manual a long time ago.  They might post it in their FAQ or support for a particular device.  A Google search is your best option to find this information..  An example search would be "limitations Garmin 64".

4.7.3 on Windows 10

Basecamp asks, and now that I'm looking for it, I can check that Basecamp will "compress" it a bit if you check "chose number of points automatically". And it will respect the number you type in. 

This seems to be a device (64ST) limit that isn't mentioned. Since Basecamp knows the device type when you "send to device" it could at least warn me. But I hear Basecamp is no longer an active product, so its my responsability