Like a lot of questions, it all depends. I watched hot tubs come into vogue 35 years ago and pretty soon there were dozens in our neighborhood sitting unused. I still use mine 5-7 nights per week when we're home. I like mine and it makes me feel better and sleep better at night.
For many years I've watched people buy things that they always thought they wanted and then they find out that after a year or two the item sat unused. Look at the iPads, tablets, e-books, laptops, boats, exercise equipment, table saws, etc. that are sitting in peoples houses that aren't being used like the folks thought they would when they bought them.
Would your TT be like those items? Maybe. Here's my take on it. If you're not sure that it would be fun or useful, then rent one a couple of times to see what type you want, and if you really enjoy it. This will give you a week or at least a couple of weekends of actual experience. Then you'll be in a better position to know if you BOTH really want one, and an idea of what style, type and size might be right for you. Do a lot of looking before you buy, sitting and talking about what items you want on your rig. And my final piece of advice is buy a used rig and take advantage of someone else paying the big depreciation on the first few years of ownership. Then if it doesn't work out for some reason, you don't lose as much money on selling it.
Wait, I do have one more thing. Buy a rig with EVERYTHING you think you'll ever want. Too many people buy a rig, pay the taxes and for the depreciation with the idea from day one that their NEXT rig will have X or Y. Buy what you really want the first time. It may happen that new things become available, the old ones wear out, and because of age and mileage the old rig needs to be replaced. When that happens so be it. But if you really want unlimited hot water, then but a rig with a Hydro-Hot and be happy everytime you take a shower instead of wishing you had one each morning. If you're happy with a 6 gallon HW heater then save the extra money and spend it on something else you really want. Buy it with the idea that it's everything you want for at least the next 10 years.
Ken