I don't think you have to spend a lot to be offered one. with that said, it really depends on the relationship that you have with your sales person. I've only started to be "devoted" to hermes 4 years ago. I went to the store and had only purchased 2 bracelets and a pair of earrings at that time. I'm pretty sure it was way less than 10K that I had spent in the store. I met my wonderful SA but I never bugged or asked if they had a birkin. To me, at that time, i figured i'd never really be offered one because A) the city where I live doesn't have an hermes store and this store was 3 hours away and i only visit it maybe twice or three times a year and B) I don't have thousands and thousands to spend on something that I don't really want in order to possibly get offered a bag. My SA asked me if I had ever thought about purchasing a birkin or kelly and I was honest with her and told her that I've thought of it but wasn't sure if I ever will be offered one. She asked me what I was looking for and within 2 months I got offered my first Birkin. This was a span of about 3 months in meeting my SA and spending I would say about 5K or so at the store. But I really do have a sincere relationship that turned into a great friendship with my SA. I think the key is to be genuine and having the mindset of when it happens it'll happen. Hope this helped and good luck with your quest.