I ended up converting a ton of my old FLV files because they just randomly wouldn’t play in some apps, even with extra codecs. MP4 has worked way smoother for me, especially with new front ends and even older players, so I think you’re on the right track converting before you run into more problems. Figuring out a way to batch process saves tons of time if you’ve got loads of files. Sometimes after I convert or mess with formats, I also have to join mkv files together for longer video sessions, and there are tools out there that make that pretty painless.