Everyone's situation is different, but I don't understand why you wouldn't do the same with squirreling away cash with your hockey stuff then either paying that to the airline at an airport or buying a single card with that saved cash when you are ready to book (if you can find a place that sells variable denomination airline cards, then you can buy one for the exact amount of the flight when you are ready to book... This is something I do with Amazon cards to buy a gift for someone on my Asp account).

Is it that your method is buying the $25 airline card when you are already buying stuff at Target (for example) so the $83.43 credit card charge your wife sees looks "normal" & the only risk is if she actually sees the itemized receipt (or finds the stash of 15 physical airline cards)?

If you are buying airline gift cards then that locks you in to using a specific airline (which may be totally ok in your situation.. but not what you want according to other parts in this thread). But, if you go this way then why keep them at all since they have no value outside of that airline and the physical cards are a risk even if they are in a place she generally doesn't look? Why not buy them and immediately deposit them with the airline when you get them (unless you plan on booking without using an airline account)?

If anyone sees and questions this (including the airline), then you can say it's your own personal savings/travel account and that "this is how I do it to insure I will travel instead of that money being used for other stuff". It seems to me that this is a better and less suspicious way of doing it than storing a bunch of $25 cards and trying to apply and use them against a single flight when you book it.

Here is a decent reference for you for working around things: https://wallethub.com/edu/cc/book-flight-without-credit-card/25851