The number of marriage slots varies depending on your Patreon tier as follows:
- Royalty: 12 extra slots (total of 15)
- VIPixxie: 9 extra slots (total of 12)
- Sponsor: 6 extra slots (total of 9)
- Top Supporter: 3 extra slots (total of 6)
You get to keep these marriage slots for as long as you're a Patreon supporter. If you fill all your Patreon marriage slots then cancel you membership, you will keep your spouses until you divorce them, but you won't be able to marry anyone new unless you divorce all but 2 of your spouses (because your marriage slot limit has been reset to 3).