We moved from the UK to Zurich in early 2010 in a burst of enthusiasm. My wife - the trailing spouse - was very keen for a few months but eventually got bored and started to find fault in the lifestyle. The language barrier didn't help.
About 7 months in, her old boss in the UK called to ask if she'd be interested in taking on some work (finance, private hospital - he was struggling to find someone who knew the ropes). She agreed and, long story short, she ended up going back to the UK. It was supposed to be for 3 months, but she's still there. We are still married but now just meet up when we can. I travel back to the UK on business once every couple of months, and occasionally we manage to meet for weekends somewhere in Europe -- or Scotland, where we both have family.
I have a decent job in Zurich and like it here. Am determined to stay, whereas she seems determined not to return. Not ideal. We're in our early 50s now, which works both ways. Seems the sort of age where a couple can independently drift on indefinitely without worrying what the other is getting up to, but at the same time, getting a bit old to consider starting all over again with someone else if that was the preferred option.
So in conclusion, at the moment I'd say that 'trailing' has definitely threatened our relationship but we're still hanging on. If I'm honest, I'm not overly concerned. The bigger problem for me is that life is more uneventful here than it should be as I obviously don't go out as much as I would as part of a couple. Still love living here though. On the plus side, the solitude gives me the chance to immerse myself in all those creative things (making music, writing, photography etc) that can seem a bit selfish in the company of others. So it's swings and roundabouts. If you don't want to be bored, you are not bored.
All things considered, I'm happier here on my own than living in the UK under any circumstances. It's still an adventure, and it will always remain so as long as I want it that way.
For others, I would advise the trailer to waste not time in making a positive effort to meet up with others -- perhaps by doing a daytime language class or learning some new skills at college or developing new hobbies in a club setting. You need to quickly feel you have some sort of social life and support network, or you're quite likely to end up dissatisfied, bored and lonely, once the honeymoon period expires.