Thomas B, yes, the problem is technically possible if someone enters an insanely long password in one program, and another program does not accept such passwords. However, the limit often exceeds the reasonable size. For example, WinRAR accepts 127-character passwords; 7-Zip 9.38 (both console and GUI) does not fail on 130 symbols.
If you memorize your passwords, you should probably stick to no more than ~20 symbols, otherwise you have strong chances to forget it. If you use a password manager, this is not a problem and you may increase the length. But 50 symbols suggested by Igor Pavlov are really many from the security viewpoint. A case-sensitive password with Latin letters, digits and punctuation exceeds 6 bits per character, so I think even 42 characters would be more than enough.
