Certainly everything in moderation - I only give letters to commands I literally type hundreds of times daily. Over the past 10 years, I've accumulated 5:
b=`bundle exec`, though this is becoming less often used and I may remove it
d=dotenv to easily wrap a command in environment variables
(https://github.com/bkeepers/dotenv)
g=git
h=hub (GitHub's extensions to Git)
j=autojump to move to common directories using just a few characters
from their name (https://github.com/wting/autojump)
