One key Momma lesson I learned was to know my audience. If there was something that I needed support on. Or better yet, there was something that I didn't need negative comments on, I'd be careful to limit the topic to those who I'd get the response I needed. If I was in the company of people who were negative about breast feeding, I'd avoid any comments about breast feeding, or being tired or anything else they'd try to relate to breast feeding. Yes, with those people we chatted a lot about weather and politics. If the conversation started to turn at all (and they wouldn't change the topic), I just got up and left with my baby. That simple. Just left. It was just easier that way.
When I needed a pick me up, I'd come here. The ladies here have saved me more than they'll ever know.
You didn't mention your Significant Other (SO). Are they supportive? Do you have anyone who's on your side? If so, talk to them about backing you up. Or even running block for you with those who are unsupportive. If someone makes a comment or starts to turn the conversation, or makes a comment - have them step in on your behalf. "That wasn't very supportive." or "I'm proud of her for doing what's best for the baby." or "She's the Mom, it's her decision." or "Well I think you ROCK!!" When negative people witness other's being supportive and positive, they tend to back off.
Personally, I'd never say "I plan to breast feed to XXX date." The reason why is that they'll remember that. When that date arrives, they'll be all over you like white on rice. I never had a date in mind, I still don't. It's up to US (my baby and I). If WE aren't ready, we're not going to. It's that simple. And really, it's no one else's business. Some arbitrary date, picked out of stress, means nothing to your breast feeding relationship with your baby.