Is 3 day treatment better than 1 day?
We can't tell you which is "better" without a lot more
detail.
For example, it doesn't matter how much more effective a 3 day
treatment is than a 1 day treatment if you can only get 1 day off.
And you haven't even told us what this "treatment" is or what it's
for, so whether or not it's more effective or just spread out
longer is an open question.