I have Paterson reels that are over 35 years old, when they were new they were kind of transleucent but over the years have turned a light brown. They have actually shrank a bit but I still perfer them for 120 film. My newer ones which are only 25 years old are of the solid white plastic and so far haven't shrank any. I've not had any problem with gunk buildup on any of them probably because I always rinse them in hot water after use. To answer you question, yes you can put them in the dishwasher. I personally woundn't boil them as they may warp from the heat. A good scrubbing with a toothbrush and any good cleaner like Comet, Bon-Ami, or even toothpaste should clean them up just fine, just be sure to rinse well and rewash them with soapy water to remove any grit.