I would never do that. Domain squatters squat just waiting for someone to come around and ask for the domain, that's why they buy them in the first place, and then they try to sell at exorbitant rates ($15k-$20k in my experience). Doubtless some companies pay that, which makes squatting profitable.

If you express interest in a domain name, the squatter knows they should renew it forever because at some point when your company makes more money or whatever you'll buy them out for the asking price or something pretty close to it. If you don't express interest and no one else does either, and traffic is minimal, the squatter will drop the domain as unprofitable (no money from the ads on the parking page, no interested buyers = unprofitable domain).