I'm an all day smoker when at home, have been since my 20's, now in my 50's.
When i go to work I cannot smoke for the full month, but when get home for a month go back to all day smoking, done this for 30 years.
A bonus of this is for the first couple of days home I can get completely baked on a very small amount.
I can say for me there is pretty much zero comedown or side effects when stopping that I notice.
Had a few periods when i stopped completely for a few months at a time just to prove to myself that i can but I really enjoy it so I start again.
Regarding productivity, I find it depends on the strain but a general rule of thumb for me is Sativa during the day which actually sometimes helps me focus and get stuff done, a nice indica to chill at night.