The steem blockchain will not extend the voting window beyond one week any time soon. It does not scale since too much needs to be kept track of in memory and as it is blockchain nodes are under strain with only 32 GB memory. We used to have votes that could be tracked for a month but that did not scale.

Also there are challenges around voting- powering down - moving to a different account - voting again types of gaming of the system. That is why the powerdown schedule and remove delegation is one week to match the vote period