My garmin 2595 when plugged into truck try's to power up but then reboots again continually. Only intermittently do I get does it start up fully but then it returns to start up procedure again

Some GPS has this problem once in a while. When it happens, turn the GPS off and restart it again. Problems should be solved.

No. it depends on your settings. You can choose fastest route, shortest route or to avoid like toll, U-turn, ferry, or..... check your settings and reset it as suitable for your driving situation.

Defeated. Go to get refund.

Have a look at this link, read the manual ...
http://www.manualowl.com/p/Garmin/nuvi-2595LMT/Manual/119452

Is the battery dead? Try it with the external power attached, see what happens. If still no go check the fuse in the end of the car charger, it may have blown.

Try a different power cord they seem to go bad after a period of time

The Garmin will tell you 'Low Battery' if its alternative power source is not available for some reason, so the battery is not being charged. Depending how the Garmin has been programmed, the display on some models will become slightly brighter when a power supply, other than its own batteries, is detected. Check for this.
It is likely that the lead you use to plug into the car is not supplying voltage to your Garmin set. If it plugs into a cigarette holder, check that the cigarette lighter works, or plug in another device to see if there is any electricity to the receptacle. Obviously ensure that the ignition switch is on. If the plug-in bit of the power cable has a light on it, check the light is illuminated. if you have a sensitive tongue, you should be able to put the end of the lead that plugs into the Garmin onto your tongue and you will feel a very slight tingle on your tongue if power is getting to the end of the lead. If not, then there is probably a break in the lead inside the plastic insulation or a problem with the supply plug.
If the plug in lead proves serviceable then you should change the batteries in Garmin as one or more may have failed and will not charge. Check for this by leaving the unit on after unplugging the external supply lead. Depending on the Garmin you have, the unit should remain functioning for at least 30 minutes. The internal batteries will degrade rapidly if the unit has not been use for some time and the batteries were not fully charged before you put it to bed.

I found my brand new nuvi 2595lmt repeatedly power cycling and loosing its charge when I tried to charge it (for the second time as well). I was using a different USB cable. When I switched to the supplied cable with the "Garmin" insignia on it, the problem resolved. Hope that helps, good luck.

the software on garmin 1300 models is atleast 3.6/7 sounds like ur update didnt take, also check in settings see if you have a timer setting for sleep mode/stanby after x time

I emailed Garmin and they recommended that I send it in for repairs