Washing weakens the bond, yet wearing for 4 weeks straight can become quite unhygienic.
How often would you suggest washing the hair system hair? I've been doing it twice a week with bio hair as well only then, but I think it might be too often.
It all depends on where you live, and how sweaty you get, etc. When I am HOT... I wash my hair/system every couple of days. I also noticed that it does NOT affect the bond.
Although, I also NEVER wear longer than 7-10 days.
I sweat a lot and go to the gym 4-6 times pre week plus a lot of out door activity, so I cold water rinse the system every 2-3 days (sometime everyday depending on how much I sweat). I shampoo every 7-10 days (or couple times per month) and deep conditioning after shampoo. My method of deep conditioning is similar like this video. Apply conditioner and put it inside the ziploc bag , put it in a small bucket filled with hot water for an hour or longer. The hair feels really soft and silky after doing this, it like a brand new system out from the box.