I say no on any meaningful scale, let me tell you why. I hope you don't mind I will use rulers in place of events, as the book keeping is bit more consistent, but I think it would apply to events as well.
The first historical ruler of Bohemia was <PERSON> (about 852-890 A.D.) the first. He is a historical figure, with several period texts mentioning him. His father on the other hand is legendary, not because he accomplished great deeds, but because frankly we are not certain who it was. Often a name Hostivit(?-870?) appears, but it is mentioned by one chronicler who combined legends with history, and some frescas, which include other legendary characters. From this example 1,152 years was enough for someone to pass into legends.
On the other hand if we look to ancient Mecedonia (<PERSON> lineage), we can get to <PERSON> the first of Macedon who ruled between 547 – 512 / 511 BC. <PERSON> names five other kings who came before him, but there are no other historical references[[1]] to them, are by all accounts they are legendary. 466
Sooo thats 2569 years for someone to become a legend.
Then again if we look in the direction Who is the oldest historically confirmed ruler? Apparently there is some debate, but since here we at least know name I will write
Me (or Ishib)-baragesi of Kish, <PERSON> of Umma and a certain HAR.TU (exact pronunciation unknown) of the city of PA.GAR (modern Tell Agrab). They probably ruled around 2700-2600 B.C.E."[[2]]
To me this implies that all rulers we know about and came before them are by definition legendary. I say this gives us an upper bound of 4722 year for someone to be legend.
But what is the lower bound? I honestly cannot find a definite answer. Both Poland and Denmark seems to place the last semi historical ruler somewhere around 900AD and since this coincides with Christianization an proper record keeping. This would put our lower bound at 1122 let. We could cheat a little and say that since we know next to nothing about Aztecs prior to about 1400 we could argue for 622 years, but here we are cheating a bit and it doesnt matter anyway.
If we say that the life expectancy of your people is 2-3times higher then ours, and a rate of legendification to stay the same. Then we would expect the earliest legends to occur sometime around 1244 - 1866 years back, but rally more like 2000 - 3000 year back.
This really got away from me, I will stop now 466