We bought in at 250 with 2 children already and now that #3 is on the way, I can see us needing more in the next few years to move up to a 2 bedroom as they get older.
I honestly have had trouble deciding on the studio vs 1 bedroom for ressies this year (our first) and decided to try one of each. The one bedroom is going to be a must for us soon I suspect as its just impossible to get the kids to sleep all at the same times for naps, etc. All that said, if I could only afford to stay in studios, we would make it work! Its all about being in such a nice place and having so much close to us to do.
I honestly have had trouble deciding on the studio vs 1 bedroom for ressies this year (our first) and decided to try one of each. The one bedroom is going to be a must for us soon I suspect as its just impossible to get the kids to sleep all at the same times for naps, etc. All that said, if I could only afford to stay in studios, we would make it work! Its all about being in such a nice place and having so much close to us to do.
I'd bet that the majority of the 90,000 owners come once a year or every other year. We bought the minimum 230 in 1992 for our family of 5. Our shortest turn arounds have been about 18 months. We always get a 2BR and some trips a 2BR and a studio for family. We have also given friends and family a couple of nights here and there. We have never caught addonitis. We're very happy with the number of points we have. We have never lost a point.
but we don't spend much time in our room when we're in WDW. I think your needs will depend on how you like to vacation. We don't cook on vacation, but if we did, we would definitely want the 1 bedroom with its larger kitchen facilities. We recently added on because we've gotten spoiled and now like the weeklong summer vacation AND a winter minivacation. I can foresee that when the day comes that we have grandchildren, we will want to add on again. I would start with what suits your needs and add on later as your needs change. Congratulations and good luck!
First my husband and I just wanted to say thank you all soooo much for all of the information! I think we learned something new from every post we read, both the good and the bad, and about the options as well! I'd thank everyone individually but I think that would take till morning to do!
Thank you all so much! 

I totally agree with you 100%. Fortunately we will not have any student loans to pay off since my husband did not need any for his schooling and neither have I. *sighs in relief* This extra money we have been saving up for something "fun" is totally seperate from our emergency savings account as well. And were definitely not planning on children until were in our late 20s and have a nice little savings set up for the nonexistent kids already. 
Then, we'd have to cut our trip lengths by 50% or double our 300 points. Maybe someday - sigh!!!!!!!!!