I went to England last week and again I noticed how my grasp of the lingua inglese is becoming stranger and stranger. I don't think it's right to say it's getting worse, because I still read lots in English and speak - mainly on the phone - in English. But I find that as I speak more Italian, I end up forming phrases in an Italian kind of way when speaking English. This is due to hearing Italians speak English too. For example I'll say "I was in England" that's not right is it? An English person would say "I went to England" not "I was in England". Other phrases I find myself saying in English are "In this period" instead of "lately" or "recently", this is because Italians say "in questo periodo."
I find myself having to concentrate more when I'm speaking English (with mother tongues) so that I don't sound too much like I'm from another planet. I wonder if this happens to truly bilingual people. You know, the ones who are bilingual practically from birth.
Apart from this little brain teaser I do consider it a great ability to be able to speak two languages fluently.
Another thing I noticed on this England trip is how I slip into both Italian and UK lifestyles effortlessly these days. I don't usually look forward to uprooting myself, mainly due to laziness, but once I get there it's like I never left. I go from having an espresso here to a tea (con latte) there, or from shopping all day there to having a siesta in the afternoon here no probs.