It says you can’t benefit from it again unless widowed. Once someone is they can benefit from it as often as they want.

Also, you could still marry someone else and have them benefit from it again.

I once played a series of all-combat one shots, in which we could use the previous day to precast buffs. Every session we used that day to cast ceremony to make the party a polycule, until the DM banned it.

By the way, the spell does not allow for divorce - it’s strictly “till death do us part”.

Which has… consequences

Wouldn’t the entire policule need to be close for them to get the bonus then? That doesn’t sound like the best tactical strategy.

The spell allows polygamy

Does the +2 stack in that case?

I mean, with resurrection being possible I think divorces would be far less often.

But especially in rich families there would probably be a lot of murdering and resurrecting, just to get out of some forced marriage.