Newer Camera

[John]

I am considering a replacement of my ist DS and see that prices on used 
K-5's are starting to go down.  Are there any lens issues I need to 
consider when going to a K-5.  My lenses have been working well with my 
camera but will I start to see defects as the lenses have been used for 
a while. The two I use the most are a Pentax FA 28-35 mm and a Sigma 
70-300 mm. I also have some older manual lenses with out auto focusing 
but they don't see a lot of use. Are there any operational issues I am 
libel to run into?    Or is there another choice that is not as big a 
jump as the K-5 as far as performance that would be a better choice?

Thanks for any information or suggestions.  I don't contribute very 
often but follow the group somewhat silently.

John G.