long-term N2 solution?

Is making a long term liquid nitrogen cooling setup possible?

Not without recharging the LN.

Not practical, but possible. Another possible use
of nitrogen is to put the PC in a dry nitrogen
sealed tank like a fishtank. Then, after purging
the tank, you could run pelts w/o concern for
condensation. All that fooling around with closed-cell
foam and all that would be history.