That might depend on the PEG itself. My second, crappy 12F PEG was prone to clog and only lasted a few months -- Part of the problem was that the end wasn't open, except for a tiny hole. My current PEG was installed in Dec08 and is still going strong (20F), in large part because it is just a tube with a large hole in the end.

In the unlikely event it should start clogging, I know I would actually be able to put a wire or stiff monofilament (weed-whacker cord) down to clean it; even the brush they sell for cleaning the drink tubes on CamelBacks.

Actually, I don't think the silicone dissolves or anything like that, just gets discolored inside by the stomach acids.

Replacement would depend on who you have do it -- When the radio-docs did mine, they just took me down to imaging area, gave me a local, and placed the small tube using a fluoroscope (I got to watch). The small tube had nothing on the end, so was easy to remove (Did it myself several times to clean it, but that's not recommended!)

Personally, I'll always go for the big tube -- More trouble to install and hurts when removed, but does the job it was intended to do.

For the bigger, better tube, the gastro-doc knocked me out and put the endoscope down my throat to install it. Likely, he would also remove the old one while you are out.