I've professionally used each for a year or more C#, Python, Javascript, Objective-C, Java, PHP, Visual Basic, and ActionScript over the years. But if you asked me to write a function in anything but the first three languages, I will almost undoubtedly stumble a bit in producing them (hell, I still have to look up syntax for Python periodically).
That doesn't mean I couldn't pick them back up in a future job very quickly again (each job I worked for I was usually contributing to their code base in a few days, never longer than a week), it just means I don't have them fresh in my head and I can't store absolutely everything in my head forever.
But you'd still probably think I was incompetent. I've certainly given that impression before when I had an onsite scheduled by a recruiter and given less than 24 hours notice for an Objective-C job, a language I hadn't touched or thought about in over a year, and was handed a laptop by a Junior Programmer and was told "Code up an app for me." while another interviewer sat quietly across the table from me and stared at me the whole time while I refreshed on a years worth of XCode changes and forgotten syntax in real time.
After that wonderful performance they didn't give much weight to the two employees in their department that worked under me at a previous startup I was Lead Programmer for and vouched for my skills.