'Over the years' is not as general as 'a long time'. This phrase refers to change that took place over a period of a number of years. We don't know how many exactly, but the context would tell you approximately how many years - usually a period between approximately 5 and (perhaps) 50 years.

Hello. Not sure if I'm the correct person to explain it since I'm just an english student but I'll try my best. In spanish "over the years" usually translates as a period of time, it doesn't matter if it is long or short, where there is no specification of the begining and neither the end of it. So, it doesn't have to be a long time, despite a year could be such a great time under subjective considerations, but it has to be inespecific. Hope it was helpful