Track Points Used
You can adjust how often track points are saved. I find the default Automatic settings are just right. (Automatic only takes a point after so much movement, more on turns, ...)
On my eTrex Vista, with 10,000 track points on the "Active" log, I typically use up about 500 to 1000 points per hour (a point every few seconds), depending on the ride.
When I save a track on my eTrex Vista, it reduces the number of points in named 'Saved" track log to under 750 total. Even for a long ride, the data reduction is very good. When I plot the two out on a computer screen they're almost indistiquishable for all practical purposes. The only downside of a Saved track is that it doesn't save the time and speed info. But it does save the altitude, so you can still plot profiles from the Saved data.
The Edge doesn't say anything about "Saved" logs in the specifications or the manual, so I think it's like my Garmin "Quest" in which you need to save all the points. The small downside is that you need need to download your tracks after every 13 hours or so of riding. - not too bad except for multiday trips. (BTW, I can store 10 data reduced "Saved" tracks with names of my choosing in the eTrex Vista.)
The Edge just came out, so nobody will have much experience. But I used the eTrex Vista on the handlebars for years, with very big G forces through thick mud, nasty rain, big rock gardens, lots of technical singletrack with drops, and fast DH runs. It's lasted almost three years now - more than I can say for my other bike components. Just for starters, I've broken two bike frames in the same time...

The eTrex has a thick case and rubberized edges. I've dropped down piles of rocks with only a big scratch across the face. I scuffed up and detatched the rubber edge a little when I drove out of a parking lot with the GPS left on top of the car and it bounced down the highway (did this two more times too over the years....

Getting better now). It also had a problem with turning off on big hits, maybe once every week or two while riding. But I powered back on and it was working fine. It was likely the battery spring wearing out over the years, because if I bent it back, it got better for a few rides. The joystick was also wearing out with age and sometimes getting finicky, but usable. Again, these are more likely normal wear issues from my long repeated use over 2.5 years. I repaired all the cosmetic problems and self-turn-off a few months ago with Garmin's nice $125 like-new refurbish deal.
The Edge should be pretty good on reliabilty, like my eTrex, even if it's smaller. Garmin builds very tough units. They rate their units for constant 8 Gs of vibration, and several feet of water depth. Garmin knows this unit is going to be used on the handlebars of bikes and don't want returns, and design for such use. If you could only get other bike components that tough...