You don't have to do the 90 one if u don't want u can just do 3 30's, i think what your thinking is if you do 1 90 u automatically get it, which you would, but you wont get it the second you pay for it, you would have to wait out the 90 days you couldnt just say pay for 90 days than switch to 30 and bam you have it.

sorry was kinda long but yeah your way would work to, just seems like alot more hassle than it has to be.