As a former Revenue Manager, I wouldn't be surprised if you get a polite "no thank you" if you ask for a special rate. First, you're asking for a massive discount. Second, it's rare that hotels will negotiate rates for individual guests. It's nothing personal. Rather, it's a better use of a Sales Manager's time to seek out corporate/group business than it is to negotiate with a single guest (who can, at best, only represent 365 room nights).

The key factor will be how you define "2 weeks a month". If that's a full 14 nights that include traditionally quiet nights like Fridays and Sundays, you might be in luck. However, if you're talking two business weeks (Monday-Thursday stays), your stays would likely cost the hotel money by displacing guests willing to pay regular rates.