I often travel solo but occasionally invite friends. It's been great for me for the same reasons as Royal Consort. I would never ever pay Disney rack rates for deluxe hotels, but with DVC I upgrade my trips to fantastic resorts.
Every three years is doable, but it has two problems:
1) its easy to lose spare points. Let's say you buy 100 points, so you have 300 points every three years. But it's nearly impossible to book a vacation for exactly 300 points. So if you just need 290, what will you do with the remaining 10? Even f you don't borrow and bank them, they'd be expired by the time you take the next holiday. You can rent or transfer them, but it's not easy and quite the effort for a small gain
2) If you need to cancel, then you'd be at greater risk of losing the points, because banked and borrowed points cannot be banked again or put back in their UY. You can rent them to recoup some money, but then you wouldn't have them for your next trip
So every three years is doable, but it's a bit more risky than every other year.