Jeremiah's seventy years

Many people come to different conclusions around the seventy year exile prophesied I. Jeremiah 25:11. Some say they were 360 day prophetic years, others say "seventy years" is a phrase to mean a generation. The dates for the captivity vary, ranging from 606 BC to 536 BC. Wikipedia and others say the exile lasted from 605 BC to 537 BC. That's 68 years. However, with those dates I've realised that, although it only makes 68 solar years, it makes 70 lunar years. I know the Hebrew calendar is lunar based, with a typical year consisting of twelve lunar months and having an additional 13th month once the first month drifted from Spring (when the first month is supposed to occur). These leap months are now mathematical, consistent, and predictable, but back in the time of ancient Israel these leap months were off the cuff, only occurring of the high priest said so at the end of the twelve months. Therefore I'm assuming there had to be some general idea of what a "year" actually was, time wise. Otherwise people will could make pledges for X years without any knowing of how many months they had pledged for. So maybe when Jeremiah prophesied the 70 year exile, the Jews at the time could've understood that as being a time duration of 70 typical years, or 70x12 months. Is this argument plausible? What are your opinions? I've looked into the Talmud for answers and it appears that there is a difference between someone making a pledge for "a year" or "this year" and someone making a pledge for "one year". "This/a year" would mean for the rest of the year, even if that year turned into a leap year, whereas "one year" indicates 12 lunar months. I don't know how "seventy years" would be viewed as in the Talmud.