I had one of those Blackburn floor pumps with lifetime guarantees: I don't know how many times I returned it to the bike shop to get a new one. Problem was the chuck would eventually start leaking and there was no way to replace the rubber grommet short of buying a replacement chuck (like a Silca head).
Last time this happened, rather than get another replacement pump, I got credit for the pump and upgraded to a Silca with the presta/ schrader combo head. Although I'm generally happy with the pump, in the relatively short time I've owned it I've had to replace the chuck grommet several times, I've had the rubber hose split on me (that never happened on the Blackburn), I've had to permanently glue the wooden handle to the pump shaft as it kept loosening, and the plastic body of the combo chuck broke off at the plastic threading. In addition, in my experience, the rubber chuck grommets vary widely in their flexibility. On one particularly stiff replacement grommet, I kept ripping the valve stem off of the inner tubes trying to pull the chuck off. On another, it was so stiff and the hole apparently so small, the only way I could use it was to drill a larger hole in the rubber.
Currently the pump is behaving itself, and I have several grommets and a replacement head stashed away in case of future emergencies. So, no, I'm not gonna sing the praises of Silca floor pumps.
Bill Silverman
Pasadena, CA, USA