Too high to get in?

If I missed the boat on Tech stocks, is it bad time to get in when they are 52 wk high such as AAPL or they have started a long run such as NVDA?

The charts for tech stocks do not go back down to allow a chance to buy and stochastics do not go back to 20 for a long while already. I thought stock goes in a cycle and it will go back down when it is overbought. Am I waiting for something that may not happen for a long while?