P.S. If it's a basically generic peace lily that's 30-ish years old, is it probably S. wallisii?

You don't need to have them in the same pot to present them together. You could get an outer container and put several plants (still in their individual pots) in it and pack the space between with peat or potting soil. I have done this using an old china bowl from a Victorian washstand. The plants growing near each other create a nice humid atmosphere. In fact I prefer plant groupings from an aesthetic point of view to individual pots. But that could be because I am essentially a gardener not a plant collector.

Ooh, that's a great point! Hmmm. Maybe an outer pot with sphagnum fluffed around/over the inner pots? Would that create any mold problems or anything? :-/ I'd like something I can still drench/flush pretty easily.

Spaths want much more water than pothos so I would not put them together in the same pot but would do as Flora suggests.

Huh. Maybe I overwater my pothoses, then. For the last year or two I've grown both in basically a slightly damp bark-based orchid mix (if I recall correctly there's some aquarium gravel in there too, and I recently procured a bag of Turface so we all know where that's heading). Hm. Well, crap.