It's bound to happen that the customer blames you for the result of their decisions later.
This is the problem and is why I never give this kind of advice anymore.
As soon as you start advising on the merits of ideas you becomes somewhat responsible for them if things go bad. If you once gave advice and then stop, but later something goes bad they will ask why you didn't say anything like you had in the past?
Don't tie yourself to your clients decision unless asked, and even then be careful. Give them a time frame and a cost, that is all they need from you if they have their business plans in order.
It's the same reason you never wave a pedestrian into the cross walk once you stopped for them, if they follow your prompt and a car goes around you and hits them who will they blame?