Seal grout after cleaning?
After cleaning grout lines with either one of the natural solution recipes here or with Mr. Clean do I need reseal them?
This is up to you. The reason grout lines are sealed, is to protect them from absorbing stains.
A sealer will help slow down the absorption of a liquid into the grout line, but at some point will deteriorate.
This is where most people don't do anything and let the grout lines become dirty and even stained.
It sounds like you are more proactive and are cleaning your grout lines. Now is the perfect time to seal them.
Remember, the sealer will not last forever, maybe a year. After about a year, or the next time you give them a good cleaning, seal them again.
Sealing grout lines is something that should be done every time you deep clean your grout lines.
I hope this helps.