toast I don't foresee necroing being a big deal. It's contingent on people actually searching before making a new thread. It's also not obvious why necroing is bad:
Usually, threads die off for a reason, mostly because the people that argued in it are now tired and have moved on, replying in one of those is akin to re-starting the flame war. But I don't see that being an issue here. In the olden days it's why mods would lock threads once they got "spent". Most forums software has an "auto-archive after X months" feature.
The other reason is, well, the people that used to post on the forums might have moved on, so you're not talking to anyone anymore, which again, I don't see being an issue here.