I wear these all the time.  I wear them both for DIY home remodeling, as well as for work as a telephone engineer.  I get in a lot of mud and dirt in crawl spaces, as well as construction sites, and attics for cable runs.  I have been wearing the same pair for 7 or 8 years, and they have held up great.  I use a soft brush and some saddle soap when they get dirty, and they come out looking good.  I think I will replace them soon though because the sole is starting to wear through and it is making noise when I walk.  I have seen a lot of guys on job sites wearing these same boots, lots of them seem to wear the leather through where the steel toe is.  I know lots of guys use the toe to rest materials on, like lumber, pipes, drywall, so that makes sense that the toe would wear through.
One thing that I do is replace the insole with a powerstep insole.  Makes them much more comfortable for me anyways to be on my feet a long time.