yes there is a point where it is useless to smoke more, but its almost impossible to do it at once, it is likely to happen when you smoke a lot over time...

The reason is you THC blood level, this is how much THC is in your blood, and it can be up too 1000, if you smoke once your level will be prob at like 25, but over and over agian it can get high, in a drug test i took mine was 535, the highest ive heard of someones being it 750 or so,

so u get the point, if you smoke a shitload of weed everyday for a while you will eventualy not be able to get high anymore, so you should stop for a while and then start up again and you will be able to get a nice high...

so...if you cant get high anymore your thc blood level is at 1000 and you should stop for like 1 and a half months, to get a nice high again