A lot of monogamous culture ends up defining “if a relationship works out” by if it leads to marriage, or if that marriage lasts until the death of one partner rather than a breakup, as per the traditional relationship escalator. In polyamory, each individual relationship gets to define what “working out” looks like for itself.
For some relationships, that might still be the full escalator. For others, “working out” might be defined in the kinds of mutual emotional support that are provided, irrespective of physical or financial entwinement. Or it might be marked by the entanglement of moving in together, mixing finances, sharing google calendars, fluid bonding, or building certain traditions together around vacations or holidays.
Figuring out how you and your partner each define how your particular relationship will work out (if you have a goal or definition to start, or if you’re both OK with going vaguely forward in a direction and have some milestones you like along the way) can be a pretty important step early on in the relationship to make sure you’re working in the same direction. Discovering that one of you is trying for a handful of milestones - shared calendar, one weekend away a year, and a tv show you watch together, for example - and the other for near-escalator patterned deep entwinement of finances, households, and parenting each other’s children can be a horrible shock if you don’t openly discuss it until a year or two in. Have conversations relatively early, and often - check in if you feel that there are changes happening in your relationship, before it becomes a conflict.
It’s a really hard question to answer - what do you want out of a relationship early in it? - Without being in a place where you’re accidentally (or, worse, intentionally) interviewing people for relationship roles like jobs. Doing that not only makes dates a lot less fun, it also limits how connections form with people. However, limiting your connections before you get to the going on dates phase - refusing to go out with the casual hookups folks if you aren’t looking for casual things, for example, can be a smart move to skip the “now I interview you to make sure you’re looking for the same things as me” section of a date and let you actually build connection, and worry about whether you have the same definition of if a relationship is working out three or six months into the relationship, instead.