Interesting reads above.
Totally agree with Wire on the answers.
If the line is supported by even action so the books make money, then his capping skills exceed the public's capping skills greatly when finding value in buying a better number.
A total of 7.5 may be the number that the book sets for even action and wins the juice in volumes of bets. But sonetimes, a great capping advantage is consistent with winning on these "even-action" lines when buying runs.
To only make a bet because of a line at -105, or to never make a bet on a line over -140 is purely consistent with a narrow capping level of knowledge, or - consistent with a limited ability to find value in any number. There are many capping systems that work for many gamblers. Most of which, are like bigger winners than losers if they find these advantages to buying points/runs etc.
Being afraid to buy runs or play lines that are larger than 140 is simply putting the capping capacity into a small spectrum and would be an indication that capping skills are inadequate beyond those numbers. Meaning that if you dont know why the lines are larger, then you shouldn't bet the game. But if you can find why the number is larger, then you should still be able to find an advantage in either the dog of the favorite. If not, then you are only guessing imo.