Filling my prescription early due to vacation?

So I will be studying abroad from June 15th til August 31st and my doctor who knew this prescribed me 2 months worth of my adderall medication even though I just filled my previous prescription about a week ago. When I went to refill the script he wrote my insurance said they do not do vacation overrides and I could not refill for another few weeks. This made me worried and I suggested to my doctor that he at least change the prescription strength from 20mg to 10mg so I could at least still get a new prescription and have it for while I am overseas. He denied this claim believing it was a way of trying to trick the insurance companies and that I'd be better off paying from pocket which would be over $100 dollars. I will not do that! Was my doctor correct in this or should I try speaking with him again? I prefer not to go 2 months without a medication I was prescribed to and feel like I need. Please help!