As a newbie I'm not sure if this is the proper place to pose a question, but let me try.

How do I know when the felt (unstudded) soles of my wading boots need replacing? I took a couple of dunks in the river last summer and now am thinking that every step seems more slippery. Am I being parainoid or is there a way to tell, maybe visually, that the felt on my boots needs replacing?