They are one of the best most robust of the GBB category
Ancorp has been running a beat up 2nd hand TM 4.3 with original slides and everything for a few months now and its still kicking it must be over 2 years old
Body is ABs but can take propane
Mags last for about 1.5 to 2 full shoots
1 mag = 31 shots
Fill it up completely it will give you between 45 - 60 shots
If you want better research there are plenty of review sites to go to that already show its good feed back
http://arniesairsoft.co.uk/reviewpost/
http://www.justpistols.co.uk/