How old is the machine, and have you had it since new? I have a Macap which is similar, and they say a couple of hundred kg's (4-5 years home use?). If they feel sharp, should be no prob.
Could it also be the grind? I find that a fine grind takes a lot longer to come out, and will clump more - you could try a coarser grind and slightly harder tamp and see if it changes anything?
I wouldn't go on time alone though… ;-)