I do a lot of theater shows that run over 1 hour per act. I've had good experiences with the Tascam HD-P2 which has a lot more features than this unit when it comes to sync. For instance, you can lock the Tascam to the camera's vertical sync pulse and there are at least 2 to 3 other methods of sync. I would have traded 2 of the 6 mic channels for these features. 4 channels is ideal for my work.

I love the DR-680 but you should read...
 

A review of my experiences with the TASCAM DR-680 at over 100 degrees operating temperature:

I chose the DR-680 because it recorded to a flash drive, I used 32gb sd cards, rather then to a hard drive, I felt the flash drive would be less likely to fail due to rough roads, airline travel, dust, and wind, with varying humidity. I also liked the 6 channels available for discreet recording. I did not need time code, as we were not using a clapper or sync time code, we were shooting on two 5d’s.

Things I loved: Portable, very light, the flash drive performed excellently, it has 48V Phantom for my boom mic (see also things I didn’t love). It ran almost nonstop for two 36 hour shifts

Things I Didn’t Love: Heat not so good! The manual says its maximum operating temperature is 104 degrees Fahrenheit. Let me tell you what happens after that. My DR-680 was in a portabrace bag with air space all around on the left and right sides, it was hugged close to the case on the bottom and had some air space on its top, then on the other side of a divider were 4 lectrosonics receivers. In the first days of shooting we were told the ground temp got to around 109, after quite a while I noticed a buzz in the boom, I turned off the 48 Volt power supply and that eliminated the buzz. I had to run without the boom for a little while to let it cool off. The other channels that didn’t require 48volt power would operate fine. A day later we had another shoot and we were fine until the temp reached close to 115, I had learned just to take breaks inside the air conditioning, but this time we had to run for an extended time outside shooting a scene. So up pops an error message that says “device error”, no other remedy would work, I tried cooling it down, the only way to get rid of the error message according to the manual was to unplug it, I lost all the files since the last shutdown. This device has to be shutdown and given time to complete the writing of the files to the sd card otherwise if you just pull the power you are not saving your files. Lesson learned, from that time on I frequently in between scenes shut down and then started up again in order to save the files.

Ed Anderson
Ronhillimagery.com

Luckily it rarely gets over 70 degrees up here in Humboldt! It is humid though.

Ed...
Do you mean turned off/powered down? The manual says it can be set to start a new TAKE if the REC button in pressed in REC mode. That should start a new take...? If the power is lost will it loose ALL the takes since it was turned on? Or just the current take being recorded?

Thanks

Doc

Re: Tascam DR680 recorder thoughts ? long sync ability ?
 

Well, I just finished a shoot today in Montana on a 13 degree snowy day. My DR-680 performed flawlessly, except the LCD screen seemed a tiny bit slow to react at times. I guess it likes cold better than heat. I have mine set so PAUSE creates a new take...it saves and creates a new file every time I pause. Never had any problem with not saving files, sounds like the heat could be the problem. I've had mine since May 2010 and had only good experiences.