I don't know too much about cryptography, but for an asynchronous communication method like email, is there such a thing as encryption overkill? For example, d

I don't know too much about cryptography, but for an asynchronous communication method like email, is there such a thing as encryption overkill? For example, does it matter whether the message takes two seconds or five seconds to decrypt/encrypt (particularly if that encryption/decryption happens in the background of your mail app)? Are there other issues as you increase the number of bits on the curve?