Since we bought onsite, at the DVC tour, I would say impulse. We had, however, spent the few months prior considering options towards preparing to "SnowBird" when we retire in 2020.
We looked at RVs, RV Parks, Mobile Homes & Mobile Home Parks, Condos, Villas, Retirement Communities, and any other option you can think of. All the financial numbers were fresh in our heads, swirling around a bit, when we found ourselves in Downtown Disney two nights before we were due to return home in October 2011. The DW was in Once Upon A Toy, and I was waiting outside, and had leaned on the desk at the DVC Kiosk. The rest is history, for us
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A very nice young man struck up a conversation with me, and gave me the basics about the DVC. When my wife came out from the store, I introduced her to the CM, and shared the information and I remember her exclaiming "A Timeshare!?; I'm NOT interested in a Timeshare presentation."
To his credit, the young man was undaunted, and revisited all the issues I had tackled with him regarding our reluctance over timeshares and, long story short, we made an appointment for the next afternoon. We found the experience very informative, and no-pressure, as compared to some terrible timeshare experiences we had been through in the past. We definitely could have been out of there in 90 minutes or less, and were not obligated to purchase on-the-spot, like many other Timeshare sales. I kept our guide working for about 3 hours; we toured every model, and even got access to a real-life Grand Villa at SSR, to see it first hand. I was crunching the numbers on my PDA the entire time, and we bought 210 points that day ! Our only regret was that we did not buy more at that price point, as we have been infected with Addonitis since. So, again, I would guess that would be considered impulse, but I felt comfortable then that it was a good idea for us, and we still feel comfortable about DVC now, 8 years later!
P.S. - we just booked a3BR-GV at SSR for the first time, and our family of 9 (DD/SIL/3Grands/DS/DIL - joining us) are going to be there in January of 2020!