You should keep in mind that you are going to lose Downloads eventually, even with bought Downloads, as accounts unfollow when they feel like it. When it comes to bought Downloads, there are a few points to consider. Fake/bot Downloads are designed to stick to your account and will not unfollow, but they can still be deleted by Podcast itself.
Bought human Downloads will unfollow you over time. This might be because they are not interested in your Podcast content. To offset lost Downloads, many providers have retention guarantees.
They will replace the Downloads you lost anywhere from a few days to a few months after purchase. Some even offer up to a two-year replacement period, and a few of the best have lifetime warranties.