We did it a weird way--we were long distance for the duration of our "courting" relationship and changed our plan at the very last second.
He lived in the UK and I was finishing college in the US, and every school break I'd go there for a few weeks or he'd come over to stay with me. When we decided to get married, he had originally applied for a K1 visa to come to the US, but the process was taking So! Long! and I was all ready to graduate and we still hadn't been approved, so we applied for visa with the UK as well, just in case. We decided we'd make a little race out of it--if the UK came through first, we'd get married here and pick up and move to London, and if the K1 came through first, we'd carry on with the original plan. Well, lo and behold, the UK one got approved almost immediately, so he flew over with his mother, we got married at the courthouse, sent my passport off for my visa processing, and packed up all of my crap and sent it off to London!
We lived there together for a few years, so by the time we decided to come back to the US, we were well established as spouses, so it was a piece of cake to get him all set up with his paperwork--and you're probably right, that was probably a huge factor in his staying, because he came over as a spouse, not as a finance.
As someone who has been through it as well, though, I'm sure you go through the same annoyances that I do about how the people on this show seem to understand the 90 days as a continued "trying on" period, when that is NOT the intention. The point of the 90 days is to give couples a teeny bit of leeway with wedding planning so they don't have to get straight off the plane and run right down the aisle! It isn't an extended trial to make sure you really want to go through with it, friends; you should have absolutely 500% decided that well before you've filed the paperwork and done all of the interviews and begun the 90 days. The three months is a little wiggle room to allow for things like sleeping off jetlag, getting acclimated to your new home country, final wedding arrangements, etc, before one of the biggest days of your lives. It also gives the couple adequate notice to provide friends and family who may be travelling to attend the wedding; can you imagine if they got their approval and then had a week to get married? That would be insane, just logistically speaking. It makes perfect sense that there is a little time built in before the deadline, but the purpose is being misconstrued by this show.
The way these people treat the process--like this is one last chance to feel things out and decide if they want to bail--really rubs me wrong because it just shows a fundamental (and possibly willful) misunderstanding of the way it is intended to work, and their abuse of the system is what made things take so freakin' long for the rest of us who were doing it right. Grumble grumble.