Most big name commercial rods sold can easily carry one line heavier. Manufacturerers do this as a sales tool, when you compare rods the first thing that stands out is the rod that casts the farthest. Custom builders have been to one degree or another been pushing for a standard way of measuring performance. The big names will not submit their rods to this measuring system, although the privatieer's regularly test them and publish the results. I have tested every rod I can get my hands on and can pretty much predict how a rod will behave when cast. I can also confirm that rods do loss stiffness over time, I have one that lost a 1/4 of a line weight in one year. That was through heavy use though. I have included a link to the measuring system for those that might be interested.
http://www.common-cents.info/
Here is one data bank site, sadly they are disappearing, for comparative purposes the ERN refers to the Effective Rod Number and the AA is how fast the rod action is. A number over about a 69 would be a fast action and below around a 65 would be med. It's a bit to get your mind around but when you understand the system it makes it very easy to get the blank you want. There are a few blank manufacturers that publish there numbers, I support them by buying my blanks from them. This system would be of great benefit to any rod, it's just a matter of getting manufacturers to publish the numbers.
http://www.sexyloops.com/eric/databa...ablesorted.php