Learn from my recent mistakes. If you have an Rockboxed recorder, in the recording settings there are settings to split by time or filesize. Mine were accidentally set to "off". Don't do that.
I went to a festival this past weekend, and setup my AKG481 > PS2/AD20 > H120 at a side stage off in the woods. I left it there running all day Saturday, without hitting STOP/START between sets. So what happened? I lost it all. Basically, it won't write a file bigger than 2gb, which is 3hr 14min at 16/44. Normally when I am watching a show, no one set ever goes more than 3hr, so as long as I stopped it before that time, it's not a problem. But here I just let it roll and figured I would split up later, when I got home. Instead when I got home, the files weren't there. I'm a software guy, and it makes perfect sense to me in 20/20 hindsight, but I didn't think about it up front. On my R4 and R09 they automatically split at 2GB, and my MR1 splits at 1gb. It didn't occur to me that this wouldn't do something similar.
Under recording settings, this is a menu "Timer Settings", and under that is "Split Measure" and you can set to "Time" or "Filesize", and then there are other menus for how much time or how big a file you want to split at. All it amounts to is that when it split files, you join them back together on your computer.