Prepaid expenses absolutely are an asset. If you were accounting for them on a balance sheet, that’s where you’d have to put them.
I agree, a Disney timeshare is an asset, but it's a depreciating asset that should be assumed to be worth nothing when you assume the risk to buy into one. With Disney moving more and more towards "industry standard" one should only assume that they will be able to buy in and have x years of enjoying that timeshare.
I appreciate the general thrust of your post (that we should encourage people to be thoughtful about buying a timeshare.) But words have meaning and when you start describing something as an investment because...
"You are putting money down in the hopes that it will save you money long term"
"[It will] allow you to take more extravagant vacations for the same amount of money"
"feeling like you own part of Disney has value to you, or any other emotional reasons"
"You’re investing in your happiness"
... you start to dilute the meaning of an investment. It's not unlike the Oxford English Dictionary adding that "literally", when used informally, basically no longer means literally.
All of those things you listed above are wonderful reasons to buy a Disney timeshare, but that does not make them an investment. I agree that one should be thoughtful about approaching what the financial implications are for buying into a timeshare. I especially agree that it should be thought through in terms of what the cost/value is to the individual buyer, but the term "investment" is being bandied about in relation to what the timeshare can be sold for in the future.
Using "investment" in conjunction with "asset" when referring to a Disney timeshare is exactly the slippery slope of buying into a timeshare with the expectation of being able to recoup an initial spending outlay. Sorry if that rubs you the wrong way, but that's why I will refer to a Disney timeshare strictly as a luxury purchase you buy to use and enjoy. Calling it an investment/asset just furthers the dangerous risk-laden perception otherwise.