67% RRP means a 33% discount. It's better than I've ever seen it sold for here in The Netherlands. Currently Amazon Germany is selling it for ~ €116 which is about 28% discount on an RRP of €160.
So 33% discount is already cheaper than what I paid for the 75105 last year when I bought one for myself (€121, or 24% discount). Oh well, c'est la vie. At the time I thought it was a really good deal, but I had just started with LEGO investing that time. What did I know about prices and how much discount is possible when you're patient? And that's where the experience of long-time Lego investors comes into play: knowing what discounts are feasable and when is the best time to strike.
Ultimately it's the gamble when you see a discount: is this the best deal I'll ever have on it, or will it get even more discounted? And if you wait too long you may not get that deal any longer and you'll finally have to buy at a higher price.
I'm sure every LEGO investor here has bought sets when they thought the discount wouldn't get any deeper, and then they saw the same set at an even higher discount a while later. Keep in mind that people love to show off and tell here about the awesome deal they scored, but will rather keep quiet about the mistakes they made.
Returning to your question: should you purchase 75105 now at 67% RRP, is something you have to decide for yourself. Other Brickpickers here won't buy non-exclusives at less than 40% discount, but that's their choice/strategy. This set will not retire any time soon, but if you don't mind holding it for a few more years knowing you got it at a decent discount, then it may be worth it for you.