The voucher system may sustain this bull run for SPS. Since vouchers are only limited to 33,333 a day, that means if you want to continue earning them you will have to stake SPS for the entire 30 days.

I think that everybody is planning their strategies a the moment to get the most out of the airdrop. There are lots of factors but most will b bought in the last few days as everybody tries to maximize sps and vouchers.