The biggest problem I seem to have with file hypnosis is the necessity for repeated listening to the same material on a daily or nearly daily basis for long periods of time. The longest I've listened to a single file has been for about a week daily. It was quite monotonous. A lot of body builders notice that if they perform the same workout over and over, they plateau. There may be an analogue for hypnosis, performing the same tasks regularly has been shown to be extremely taxing for the psyche.
So, if you have the same problems with monotony that I do, try this:
1. Make a long list of all the files you want to try out, whether you're serious about them or they're just a passing fancy.
2. Re-name them so that a number is in the title, and each file is a different number.
3. Use a random-number generation program or site before you take your daily listen, and listen to the file that corresponds with the provided number.
Depending on how many files are on your list, you can either trim the list down, or you can come up with a scheme to "weight" critical files so that they come up more often. You'll want to get your most important files in at least several times each week, but not so often that you get burnt out.
For this to work well, you'll want to trim your files so that they're only bodies, and find your favorite induction and awakeners, and use those as bookends on your playlist. If you have a particularly large list (or insist on listening to some files daily) then you'll probably have several bodies in each day's list.
Let me know what you think of this, and what seems to work best for you. What I've suggested here was just a random idea that popped into my head, you'll need to play around with it a bit to get it to work for you.