I am a working/pumping mom. With ODD (now 4), I was home and gave her a very occasional bottle (like once every few weeks) starting around 6 weeks b/c I knew I wanted to go to a friend's wedding in another state when she was almost 5 mos. It was fine. She was fine with the bottle, loved the boob, took bottles of EBM when I returned to work at 10 mos, and continued to nurse until she wasn't interested anymore at 16 months which, while some might consider "premature," was fine for me.
With YDD (6 mos), I returned to work briefly when she was 11 weeks (I'm a teacher and had to go back for 3 weeks before summer vacation). She was not psyched about the bottle. I had been too busy and a little lazy about giving practice bottles mostly b.c I hate cleaning pump parts and it always seemed difficult to time. It was very stressful for me and for DH who was watching her. Yet, we made it through. I took the summer off from pumping, lost my freezer stash during hurricane Irene, went back to work and DD adjusted to bottles again though she is a reverse cycler and seems to take most of her milk from the breast when we are together. She takes about 10 oz when I am gone.
I don't really think it matters much either way. For me, it might have been less stressful if I had given more bottles early, but it's all fine. DD is a chunky 6 month old EBF baby who will take her milk from other sources when mama's away. I am conservative about pumping b/c I too find that it triggers oversupply. That said, I could not have returned to work at 11 weeks without the freezer stash I built up by pumping 1 side each morning. This gave me the confidence to know that DD had what she needed when I was gone.