I don't even know if Cosmo lets you link accounts or not. But for this analysis, let's just say you always travel together, and it's a question of whether you should put all of the play on one account, or maintain one account at Gold and the other at Sterling.
You say you earn 10,000 points a trip, but you don't break out how many are from gambling and how many are from hotel spend. So let's just say it's all from gambling. And let's say you won't make Platinum even if you did all the play on one account.
Two of the main benefits of tier are the points multiplier and the bonus comp nights (one for Sterling and two for Gold).
The thing is, if you're only going for weekend trips 3 times a year, you don;t even need to use those tier nights - if you're earning 10,000 points over a two or three night stay, you must be getting 3 night offers anyway, with enough frequency that you can use those offers to book your trips without touching the tier award nights.
The multiplier for Sterling and Gold are both 2x, so you're not gaining or losing anything there by allocating your play one way or the other.
So it's hard for me to come up with much of a meaningful advantage to maintaining one account at Gold and one at Sterling, and it's also hard to see why not. I'd say, maintain separate accounts, IF:
- You think either of you might make a solo trip. If you're only getting offers on one account, that person has to be there to check in (as far as I know).
- You think you might be in a position to use all 3 of the tier comp nights to do extended stays (ie. stay an extra night on each of your three trips.) Keep in mind that the tier comped nights are "wild cards" in that you can tack them onto a marketing offer, BUT, the casino is still going factor in those nights in your overall player rating.
- Similarly, two accounts and therefore two simultaneous marketing offers sets you up to back-to-back his/her offers for an extended stay.
If you were going to go the separate account route, I would say get one account up to Gold first, then get the other one to Sterling last. The reason for that is that getting to Gold first gets you the daily 2-for-1 at the Wicked Spoon benefit faster.
If you play at the same level consistently each trip, I don't think playing on a single account will get you better offers in terms of a better room type. 10,000 points on a two or three night stay is going to get you pretty much the same offer every offer cycle, regardless of how many times a year you do it.