This is not a language that shares any traits with English. It is hard to get going, and the vocabulary takes a considerable amount of time.
You can't switch to Finnish at work, as you simply would not be able to get by, and you can't do it at home as it changes the dynamics of your relationship. This is not an excuse, it's reality.
That's what I was trying to say. If you do want to learn the local language, you have to be willing and able to put up with it being pretty crappy for a few months. My experience has been that it's very hard to integrate a new language into your persona without immersing yourself in it. For most people it's not worth it if they can get by without. Completely understandable.
Now you've got me wondering if I should start thinking about how to teach Finnish to English-speaking professionals :D
Finish kids don’t need ten years to learn the language either, do they?
So I think in this context of a professional—who likely has a family—coming over to work, deanclatworthy is right.
Expats are most likely are in an English-speaking environment at work, where speaking Finnish at the level of a four-year-old is going to be a bit of a hindrance; no practice at home unless they have a Finnish partner, and no real options for social activities that will tolerate the learning curve, like children have.
And if it is anything like the Netherlands, any mistake you make will instantly and irreversibly switch the conversation back to English.
Children learn the local language, partly because of immersion, but also because they're corrected nearly constantly when they begin to speak. We forget that when they're capable of "good" communication.
I'm seeing interesting things here, I speak to the child exclusively in English and as far as he's concerned I speak/understand zero Finnish. I'm hoping I can start speaking more Finnish in the near future, he should be able to understand I'm "mostly English".
One obvious thing that really drives the language home is the notion of pronouns. Finnish has no gendered ones, so when he speaks English to me he'll be "Mummy is asleep, he will wake up soon?". I have to keep saying "Mummy is a girl, we say she". I've been doing that for 8+ months, and he still doesn't get it right. That's the level of repetition that's involved in learning a new language.. and even now it hasn't "stuck".