Though this post is very old and he is not active now.I am replying because of his posts.
The bes time of selling your altcoins is the end of every year . Always in this part of the year altcoin rich ther maximum .
Your answer is wrong mate.Best time to selling atlcoin end of the year? Why? best time sell altcoins if you are in profit and you dont want to take a risk.Also if you bought shit coins or scam coin then try to exit as soon as possible.
It is good to sell an altcoin when the price of bitcoin is going up because the alts price will surely go down and majority are selling it. And holding altcoin for a very long time is not good because the value will surely plummet every month if there is no good news about the crypto.
Also halving is near that's why its much better to buy bitcoin than altcoin today.