When is the best time to buy ALTs? Now!
Don't go all in, split your funds into four in case there is a 5% drop in BTC price which would give a 20-30% discount on ALTs.
Be ready to hold for at least three months or till when you have gotten a significant gain.
Don't sleep on it. You can't time the market.
What you can do is to position for the market pump (buy and hodl) and sell for profit.