It is said that you should at least touch of your hair every 6-8 weeks.  Why did you choose 4 weeks?
I like to go about four weeks because my roots start showing.
I know perm salts and hair dye chemicals can damage your scalp.  What conditioner do you use to help with this?
I use salon based products. Loreal conditioner and shampoo.
I read that it does a great job of infusing essential nourishment into the hair.  I wonder how long one bottle lasts?
It can last about a month especially if you use small portions.
I see.   I have been told Pantene Pro-V is good also.
It's alright. I use Tressme before Pantene.
I heard that Tressme has a lot of sulfates in it.  Is that correct?  
Possibly but it works well for my hair.