The GPS system is probably the last system to fail, since its mid-level orbit and is used by the military... And even if it did stop getting maintenance, it'd still be reasonably accurate for a few weeks/months.
I bought a colorado a few weeks ago, and loaded some topo maps on it for camping. Good luck finding newer piratable maps, best i could do(as far as legit garmin ones) was 2009. Ibycus also has a map package out but it has not been updated since i think 2004.
As for the unit, dont look for ones that use dedicated rechargeable packs. They will stop holding a charge after a few years. Standard AA will always be available. Id recommend you get the GPSmap 64. It seems to be the most feature rich, modern one, without stupid BS like a touch screen(Not a good thing) or running a bloated OS(android on a dedicated GPS is a horrible idea.)
The etrex(non touch) series is also good. The Etrex 10 is ONLY waypoints(no map) so if thats all you need, it might be good, but at that point you might as well save even more cash and buy a used foretrex 401, which does the same but has the option of using a bunch of military standards.
My setup is pic-related. Use the colorado for maping, and the foretrex for navigating. The colorado has something shitty like 12 hours of battery life. Foretrex has over 20. Both can sync up waypoints and routes between them, and using the foretrex is easier since its screen is far more readable, and its easier to glance at it with it resting on my wrist.