I think that David Sear stated that copper/bronze coins tended to circulate for 100 years before they are out of circulation. That seems very likely because I have seen some weird coins of byzantine Syracuse, where folles of Anastasius/Justin I are overstruck by Heraclius. Keep in mind that Anastasius/Justin I lived about 100 years before Heraclius. I am wondering: How long did silver and gold coins circulate?
Gold, I´d guess not much, it can´t support too much handling. Silver, well that´s a totally different matter. They did circulate for centuries! For example, I can recall those "legionary" denarius that Marc Antony issued back in 32 BC, they are still found in hoards from the severan period (early III century AD). So I woudn´t be surprise to learn that some coins circulated longer...
Antony's denarii were struck on debased silver to the point that most people spent them and fewer included them in savings until the alloy caught up. Few other coins stayed in circulation that long.
Sometime in the late 1980's I acquired part of a hoard or Roman denarii and antoninianii unearthed in the U.K. The most recent coins were of Gordian III. I did not think that even these coins of Gordian were in that great of shape to warrant keeping. It is possible that the hoard was deposited well after the reign of Gordian III. So I sold all but one of the coins an antoninianus of Macrinus which I have since sold. To make a long story short in this hoard was a very badly worn denarius of Marc Antony as well as a denarius of Hadrian and some Severan denarii. Even if we can assume that the hoard was deposited some time in 240-250 A.D. this would make the Hadrian just over 100 years old and the Antony something like 270-280 years old. This is the Macrinus antoninianus I sold awhile ago from this hoard
Gold coins did not circulate as a rule. The were exceptions, but generally they just got shipped from one government's treasury to another.
