What eyore said. Induction recording is pretty particular. You really need to be just about right on top of the signal. Typically this means the speaker coild, but you can also get a decent signal from the wiring leading to the speakers. It's tough because often you can't see the wires so it's a lot of trial and error.
The orientation of the induction pickup in relation to the speaker coil makes a huge difference.
After all of this, you will probably still have a decent amount of hiss on your recording. This is probably a combination of the quality of recording device, induction "technology" and the source. Post processing may be able to help, but if you don't know what you're doing you'll destroy the fidelity of the recording.
It's a trial and error thing. I have be doing it for a while and still have a bunch of problems. Lately, while on vacation I just don't have the time to experiment anymore. I did the Everest BGM loop that's been posted, it's about an hour and 15 minutes, but I recorded much more than that to make sure I got a loop point (I think I did but can't remember right now). I got lucky on that one, I'm sure it's possible to get a better one right now, knowing what I know, but I just don't have the time to try. Others have done 5-6 hours for a hour long track and still have what they consider a mediocre recording.
Each speaker is different in terms of quality and levels. You might not realize you set your levels wrong until far into the recording. So, you reset your levels and try again.
Many of the new loops are hours long! I tried the Animal Kingdom Lodge Villas pool loop and I think I heard it's like 6-8 hours long. I didn't get it all, but I did get a bunch of it. I believe that there's a shorter loop of about 30 minutes played over that, making multiple attempts useless for stitching the entire loop together.