On the product listing page where entering info for digital product, it has 2 boxes:
Number of accessible days – by default , number of days is zero which means unlimited access to the file for the customer
Number of downloads – by default 0 …
Is (b) affected by (a)? i.e. if I want only 1 download and have selected that , but leave (a) at zero – does this give them “unlimited access” or does it mean they have unlimited time to access their limited 1 download?
Yes, they are related.
A) Number of accessible days= number of days before the download is unavailable after purchase. So if they pay and forget to download and you set this to 1 day, you’ll likely be asked how they can get their product because they didn’t do it in time!
B) Number of downloads - this is the number of times they can download from the marketplace using the link they get given after purchase.
So yes, if you select “1 download” and leave the second to unlimited, they will have unlimited time to make that 1 download.
I think this is a good way to go and it's what I do with my own digital products.