If I only occasionally brew at home, should I keep instant or grounds (or something else)? Related: Is it a good idea to keep a coffeemaker if I only occasionally drink coffee?

At home, I produce less than 2 cups of coffee per week. Lately, I've been using instant to keep the hassle-payout ratio favorable. (hassle such as the actual process of producing one cup, as well as storing the requisite equipment)

If I were to buy ground coffee, it would take me months (or longer) to finish even a 10oz tin.

Is it better to keep fairly old coffee grounds for that occasional cup, or to use instant coffee?
I've been that person - I kept ground coffee forever. The difference in taste between fresh and old ground coffee is enormous, but so is the difference between old grounds and instant. It's just a completely different beverage, so I would say if these are your two options, it's just a matter of personal taste (I would go for old grounds).

If you're up for it, I would buy a small manual grinder and keep whole beans, it makes a world of a difference in taste and you can keep the beans for months without deterioration. Adds a bit of work to the process though, and depending on your coffee maker would require a grinder with different abilities (espresso would require much finer grinding degree than let's say a mokka express).