2003 Infiniti G35 Engine smokes on startup

My vehicle was smoking on startup. Whether, it was cold or even when it is warmed up. It only does it on startup, regardless how long the car has sat.

I took it in for an inspection and the mechanic said that it is the valve seals. Also, the guides could be damaged. Apparently, the previous owner did not maintain the vehicle well.

I paid big bucks for an engine tear down. They basically pulled the engine, the machine shop changed out all the valve guides and seals (which they said were damaged). At the same time, I had them do the gaskets, timing chain, guides, etc.

I just received the car back about 1 week ago. The car still exhibits smoking on start up. Is this residual left from the prior to changing out th valve seals, guides, etc. Actually re-building the top half. Will the smoke eventuall go away? How long do you suppose? I was told by the mechanic that the car will still exhibit some smoke on start up for an undertermined amount of time, due to lot of sludge in the engine. They recommended using BG Quick Clean and BG Motor Oil Additive for 12,000 miles. One application every 3,000 miles. I also changed out the exhaust and tail pipe to see if there was some residual left over. How can I get the car to stop smoking. The car runs fine now, however, the smoking is annoying and embarassing. The mechanic did say eventually it will go away. How long do you think? I paid over $4,000 for this big job and it is annoying. I feel that paying all this money, the problem should've been solved. How long should I give it before I call the mechanic back, and say that the problem still exists.

Thanks for your help.