does it hurt a receiver and transmitter battery if you leave them plugged in for along time ,say several days i have a dx7 transmitter and a spektrum receiver and i work away from home and i want them charged when i get in on the weekends

That depends upon the capacity of the RX and TX batteries along with the power output of the charger.

What does your charger put out?

You'll get many opinions on this but I know many flyers that use the "wall-Warts" that come with their radios on the batteries that come with the factory provided batteries and plug them in when they get home from the field and forget them until they go flying again and all is well. Maybe for weeks at a time or longer. Use a different battery or different charger and all bets are off though.

I doubt the wall charger will do any damage to the battery since it charges at a pretty low rate. I'd be more concerned about safety. I generally charge my glow plug igniters with a wall charger overnight before I fly. One evening I walked out in the garage and immediately notice the burnt electrical smell. The wiring and charger had melted down and getting very hot. Luckily it didn't start to flame and burn down my house. After that I just don't care to charge any kind of battery unattended regardless of the battery chemistry or charger type.

Spend about 10 bucks and buy one of those 24-hour electronic timers that you can set to turn your lights on and off at certain times of the day.

Set it to go on for an hour, then off for 11 hours, then on for an hour, and off for 11 hours. Then just plug your wall wart into it any time you leave for a few days and you'll always be topped off.