I'm once again looking into HDSLR for video. I'm looking into it for interviews but also lecture type events. Can I buy an XLR adapter and record, say, an hour continuous on this camera? What's the max time this thing can continuously record for? Will it overheat?
There is no recording time limit on the GH4. It does span the clips, so you'll have to cut those files together in post. I did a 40 minute wedding last weekend and it worked fine without any heat issues. You are only limited to the size of your card. Just to be safe, I would be sure to get a higher quality card to avoid hiccups.
As far as XLR, make sure the XLR source is pre-amped. The GH4 won't take care of that for you.
I'm pretty sure there is still a 30 min. limit when in PAL mode. It's a universal camera though, so you can just switch to NTSC and shoot in 24p. 24p is a worldwide recognized frame rate, so unless you're shooting for certain people (i.e. BBC) you should be 100% good to go.
The GH4 can record continuously until the memory card is filled or the battery runs out of juice (whichever comes first). There are no issues with overheating. You can check out this post for some other features that separate the GH4 from standard DSLRs.