Have you considered trying something like a subscription as a donation option? Assuming a limited pool of donors, then out of those, some people might be willing to give on a regular basis. Continue to give comes to mind as an option, think they do church/missionary/non-profits but there could be better.
Thank you for the suggestion. I don't want to "force" anyone to do anything with subscriptions, since people could be surprised when they might be low on cash, etc. Nor do I want to "charge" for these, since ... someone could download it and decide that either they don't benefit from or have the time for audiobooks ... or they just don't like what they heard and it doesn't benefit them.
Also, if I offer a subscription, then I would conversely be under some obligation to produce a certain amount of material each, say, month, or other subscription period. If I offer a monthly $10 subscription, I would have an obligation to produce a certain amount of material each month, so as not to be "ripping people off" ... and I cannot commit to that given that I don't have enough revenue coming in to be able to commit any given amount of time to the endeavor. That is in fact my hope with the donations that, say, I have enough coming in for me to drop part of my second job, and take those hours that I no longer need to spend, and in fact spend them on producing more books.
But, not getting any donations will not deter me from producing them, so that at least some could benefit from them, even if they can't donate, and I also find value in them for myself and for my family. It's just that ... they will be produced at a much slower pace.
As I mentioned, this is not a "for profit" type of venture, where I'm hoping to "live large" off of it, where if I did receive revenue that exceeds what one might fairly collect for the effort and time and investment involved, then it would be either "reinvested" into hiring others to work on more books, or else donated to the Church and/or to the poor.