I think this is your problem. I have used the Garmin GPS units for years, and have not had the problems you are describing. But, I keep mine on the dashboard of my car and keep it turned on all the time.
I think your problem comes from keeping it in the glovebox and only taking it out occasionally. It likes to know where it is and it can't update its location when it is turned off and in the glovebox. DW and I have five Garmin units between us, one in each of the vehicles we drive even a little. (Her car, my car, son's car, sports car, 4x4 hunting truck.) I have had the problems you describe, but in the past few years they have been very rare. Maybe once per year, always in very rural settings.
The unit in my hunting rig even works on the Forest Service roads way out in the boonies.
OTOH, I almost always either look up the address of someplace I want to find, or if I want to find a store by name, I wait until I am reasonably close to the store to search for it. I never expect it to give me an intersection, only a street address. Don't expect it to be something it is not meant to be.
Get a bean bag mount for your Garmin and keep it on your dashboard. The newer models will show your speed and the local speed limit. This has saved me enough tickets to more than pay for the unit. The speed indicator is far more accurate than the one in your car. I connect mine to my Mac every few months and update both the software and the maps. From the reviews I read, there is no better car GPS than the Garmin.
Thanks for your input. The reason I keep my Garmin in my glove compartment is because people in NYC (even nice neighborhoods like mine) have had their windshields broken by thieves after their GPS. I have a beanbag mount so that there is no tell-tale windshield mounted mount to entice thieves to look for the GPS.