Have heard that the solution will eventually clog the pores of the cedar in the humidor causing an ever increasing problem with keping the RH at the proper levels. Does anyone have any insight?

I don't know if diffused PG will clog pores in wood over time, but if they did, it would only make RH regulation easier, not more difficult. Some humidors are completely sealed with laquer both inside and outside. Many in fact are plastic coolers which are hyper-sealed. You can humidify cigars in a plastic cooler, remove the humidifying device, and the RH will remain constant for weeks, even months. I have heard ammonia might accumulate in a hyper-sealed environment, but any wood box, PG or no, is likely going to breath enough to mitigate ammonia build up.