Long term memories being so clear

Lately, I seem to be remembering things that happened many, many years ago. It is almost as though, while I'm losing my short-term memory, that my long-term memories are somehow moving forward in my brain. It is very weird for me to deal with this. Some of these long-term memories are things that I haven't even thought about for many, many years, but for some reason, I have been thinking about them again. I am very aware that they are old memories, so there is no confusion that they are happening now. I noticed that my long-term memories are very detailed and sometimes my short-term memories are lacking details.