Q for tax specialists

I am an American citizen who has been living in Europe for nearly 30 years. For most of the first 20, I filled out my tax forms. I have never owed taxes in the States, but filling out the various schedules took a lot of time, as did verifying exactly how many days I spent in the US. Looking back, I realize I could have been a bit more organized...

On to my question. I think the last time I filed my taxes was 2011. I am sure that I have not owed any money, but trying now to figure out the exact dates I have been in the States each year is likely impossible. Since I am eligible for soc security, I imagine that means I should bring my tax forms up to date. Is that true, or shall I just file this year? If I should file more, is there a shortcut?

Thanks!