You're absolutely right, no stock just keeps going and going up,...

You're absolutely right, no stock just keeps going and going up, it has to have a drop at some point. I think what we may soon find, is the point that it may drop to becomes higher each time, almost 2 steps forward 1 step back, 2 steps forward etc. Higher highs, and higher lows. Growth.

What you need to decide is your risk tolerance. How much can you afford to lose if it were to all go pear shaped? You need to decide future potential - will the share price be higher in 6 months, 1 year, 2 years time? ... so you'll need to decide your time frame also - Do I want a return in a month or am I prepared to hang around medium or long term to see what happens (refer 1st point) ?

No one can answer these questions for you, but if you can assess your risk tolerance then it becomes easier to take the plunge, or simply walk away.