The cool thing about it is that you don't open a whole bottle, but each tablet individually... so it lasts longer.
I buy mine at Whole Foods or Central Market for around 13 to 14 dollars for a box.
This is just the brand I have found to be the best for me after much experimentation (and money). However, it you like another, and it works, that's great!
I haven't heard of Natol... but, again, if it works for you and it is effective througout its life, then your set.
Best! Shanna
-------------------- "The most wasted of all days is one without laughter." -- e e cummings