I`ve never heard of that, but it sounds feesible. as for the over smoking, or higher you get, yes, you can only get so high.
there is no possiblity of overdosing smoking cannabis.
you would have to smoke over 500lbs in 1 day to even come close to overdosing.
but as far as smoking the same strain all the time,,your body will build a slight tollerance and you wont feel as high, so variety is a good thing