Wood resin on saw blades
Whether pitch collects on saws depends on the kind of stock. Softwood is very resinous and exudes copiously. Plywood rapidly cakes up a crosscut blade. A little wood resin build up in the crevices is normal if it is not in the way. As a gullet gradually clogs, its efficiency diminishes and the overflow rubs on the plate.
Warmth makes pine sap flow. It is a stiff rosin that can shatter in the cold winter, but it is malleable or runny as syrup in the warm summer. Many substances have plasticity dependent on temperature. If you put a stiff blob of sap on a shelf in a cool basement and waited a few years, you might detect a negligible sagging or migration. But when it is sawn, there is a lively transformation. The rubbing warms it up and liquefies it. Pine sap oozes like sizzling tar. You may not often cut through glue, but sap behaves similarly.
Clogging is correlated to declining performance, and is often blamed for it. It is noted that it insulates and keeps warmth in. But after removing a layer of resin buildup, if you keep using the clean blades, they can get warm anyway. Bluntness rubs and brings on the warmth that makes tar gummy in reaction. Buildup is a symptomatic effect.
Rubbing raises the temperature. When a resinous, acrid aroma wafts off it, you can assume a saw is past its prime, if not already fried. It would be odd to find one with blackened resin baked on, which wasn't also blunt. Wood resin from cedar may be acid, but it's not always an issue. Rubbing is not visually obvious, but it can be so destructive that it merits attention.
Should I remove pitch?
Poking and prodding at the plugs clogging the gullets is taking chances. A tip's not meant to endure scraping or prying. You can also wreck it by trying to sand off the baked on tar.
Some have tried to remove pitch by dissolving it. Common household chemicals used for scouring the sludge are simple green, TSP or mineral spirits. A few enthusiasts go so far as to dissolve it with caustic oven cleaner, but such a powerful remover could make quite a smelly laboratory experiment requiring ventilation. Soaking it overnight covered in an acid or base liquid might eat away the crud impressively, but unfortunately a harsh solvent continues gnawing and corroding the binder in the carbide tip. Lye silently infiltrates and compromises it, and makes a horrid stench. As soon as a solvent is done cleaning, unless every crevice is promptly protected by WD-40 or paste wax, rust begins to bloom with a vengeance.
Plain boiled water or coffee can remove resin without making a flammable, toxic mess to dispose of. If you decide to go to the effort of cleaning a saw blade, removing pitch when it is fresh and gummy is not so bad as trying to strip it off once it has dried into brown varnish.
Improvement is perceived relative to how thoroughly clogged it was. A brief dip and wipe won't do much harm, but don't expect cleaning alone to make it like new. When you use it and it warms up, the tar will return and build up faster.
Vulnerable components should be set aside before soaking is attempted. Cleaning router bits involves steps of additional complexity and special concern.