We feel that way at 430 pts now. We have enough not to steal from Peter to pay Paul. (i.e. all the family can go for a week one time of year and we can go solo for another another time of year, or we can go for about 4 weeks a year solo if no one's up for Disney).
My next add-on is purely about the resort and my expectations for availability there. We can do without the extra points just fine.
We got our fill of Marriott too. 4 weeks there, enough for each of my parents' kids, and we're done. My dad still wants to go on presentations when we're in Orlando, but I always quash any buying. My reason is that we have more than enough for him to use as well as leave to his family. In fact, he's continually banking a Marriott week a year and only using 3.
I think having enough depends entirely on how much vacation time you get and the size accommodations you need/want. We're ok with studios so we can easily stretch points. We only get a 2bedroom if we're taking people with us. If you intend to take the family and must have that 2bedroom, I expect you'd know it was enough when your annual dues rival your home mortgage.