rsvp date for Destination Wedding

We're getting married Puerto Rico in late July. I've drafted our invitations and have the "RSVP by" date set at June 14th which is exactly 6 weeks from the wedding. My fiance wants to move the RSVP date up to May 1st which is 12ish weeks ahead of time because he'd rather know sooner than later the amount of people to expect (for vendor purposes). His reasoning is that 3 months out most people should know whether they're coming or not since they'll need to take time off, make travel arrangements, etc. My question, is 12 weeks an unreasonable amount of time to ask for an RSVP to a destination wedding? We planned on calling to verify those who don't RSVP by whichever date we go with anyways. I just know from everything I've read here, 6 weeks is typical.