I need to be careful in answering this question, because you may not be asking what you appear to be asking.
First – what you appear to be asking. What I do and not what someone else might do? This is important because every part of an investment plan is related to the other parts in the sense that it is a balance of risks. What I do may be quite different to what someone else does who is also an investor. And of course someone who is a trader will probably give a quite different answer.
My answer for what I do is that there is no practical limit. This may surprise you. To understand what I am saying you need to appreciate that my investment plan calls for stocks that are undervalued (value model) or not valued much higher than the market average (growth model). So long as a stock meets those parts of my buying criteria, the price is not an issue. I know the current price is value or I would not have reached the point of buying it.
Another issue for me here is that I am happier if the stock is tending to move higher than if it is hovering. Which of those two is the strongest stock? – a no-brainer .
Second, so that is what I do. But you may have meant what should you do? I am sorry, but I cannot answer that question. I have no idea whether you are a trader or an investor and I have no knowledge of the rest of your investment or trading plan. Depending on what you are trying to do, your answer may be much different to mine.
I know this is not much help, if that was your question, but I cannot answer it for the reasons I outlined. In addition, what you would be asking for is advice and I am not licensed to advise you. So, we need to leave that question there.