Dogecoin is indeed a good choice for a long term investment. Besides being cheap, it also has good volume.
For me investment does not see when the coin is launched, but I prioritize trading volume, because this proves that the coin is selling well in the market or there are still enthusiasts.
Apart from that, you should also see if the coin is also listed on many exchanges. Because if the coin is only listed on one or two exchanges, it is likely that the coin will be lost in circulation. Will not be active. Maybe I'm looking at Blockstack right now, this coin has good potential. At the time of the Airdrop launch on Blockchain.com the coin price was $ 0.1 and the current price is $ 0.28 with chart conditions mines 6%. It's a new coin, but promising.
But for old coins, I think Dimecoin is a good thing. Apart from having daily volume, their site is still active as well. This means that the developer of this coin is still running the project well.