My DS1 was also very dummy dependent at 2.5 and wanted it all the time. I thought he was going to have it forever, lol. I would also suggest trying to limit it to sleep times if you can, but I tried that with my son and it didn't work for us. We had just had a new baby at that point so we decided to wait though until he was 3. Then we did lots of talking ahead of time about getting bigger, when you get too big your dummies won't work anymore, etc. Then one day, DH took him to the toy store with all his dummies and he got to "buy" a really special toy with the dummies. There were some tears when the clerk took them from him and the car ride home, but he adjusted well. By the third day, he didn't ask for them anymore in the day, and we did have about a week of rougher bedtimes but DH patiently stayed with him while he fell asleep to help with the transition. Overall it went way better than I expected!