The best time to invest is when the market is on trend and the coins are hot, then that is a good time to invest because if you invest on a hot market and it means that the coin has a high possibility for the price to increase even more because one of the reason why people are investing is the volume and when a coin is active and hot then the volume is big so it will be easy for that coin to increase price and you will gain profit.
well, like you describe te situation now we have 2-3 hot alts that have hot market situation...and this happened in past also and after some days going back to normal. and after 1 month the same scenario etc etc... but bitcoin is hot for many years now
some times more some times less but in general is the most hot coin ever
TO DA MOON
People just follow the flow of the money. If altcoins are going nuts, which is exactly the case right now, people go nuts as well.
Something that has been contributing to this are the destructive speculations about Bitcoin Unlimited to fork Bitcoin with a chain split as result. Most of it is all fud, but people tend to take everything seriously so easily.
Aside from the hype around altcoins and people looking to hedge Bitcoin, it's Bitcoin's higher price that makes people look for cheap alternatives as they feel their opportunity with Bitcoin is more or less over.