4 personal rules for buy and hold

You've probably heard a hundred times that you should buy and hold. Or buy great companies, then sit on your ass (Munger) or that investing is transfering money from the impatient to the patient (Buffett). 

I agree with that. However, a sentence related to buy and hold implies some facts. 

1- You have to hold really good companies. To be sure that you own a really good company, you must be able to compare that company with hundred of others. And you have to be able to understand that this company offers something unique, or, at least, something much better than many companies. The beginning is usually a great track record. 

2- You have to follow that company closely. If growth slows down, you have to be able to understand if it's temorary or permanent. A good way (but not efficient 100% of the time) is to look at competition. Are all competitors affected the same way by a slow down? If the answer is yes, then the problem is the economy, not your company;

3- A real "buy and hold" company is a company related to something that shouldn't change with progress. Waste management companies are a great example. Whatever happens with the electric car, with Google, Facebook, humans will always produce waste, and more and more waste every year. Railroads are very good too for buy and hold: there will always be transport of merchandise.

4- If something stinks, like something related to integrity of management, fraud, or stuff like that, the company should go on the hot seat. It may not always be the right thing to sell. However, I'd rather be safe than sorry. You should too. 

These are my 4 personal rules for buy and hold. If I own something that I like, I try to apply these rules. And yes, there is nothing related to the valuation of stocks anymore. It matters, but not as much as these 4 rules. Of course, a PE of 100 or 1000 is crazy, but sometimes, it may be a good idea to own one of these stocks, for a slight part of your portfolio. 

Any other rule suggestion?