It usually activates instantly. I have used the key on two different personal computers (a desktop and a laptop) simultaneously, which is allowed under their "personal use" terms. This flexibility is excellent for photographers who edit on the go.
Finding a "Negative Lab Pro License Key" through unofficial channels is risky and generally doesn’t work. Negative Lab Pro uses a that validates your email and key against their servers in real-time [1, 2]. Why "Free" Keys Are a Bad Idea Negative Lab Pro License Key
If you are looking for a "free" license key, be aware that Negative Lab Pro uses a robust activation system. "Key generators" or "cracks" found online are almost universally malware or phishing scams It usually activates instantly