One very important reason for wanting to be able to remove a tip guide is
the possibility of wear or some other form of damage. A badly worn or
grooved tip guide can chew up a flyline in no time flat. On a couple of
occasions I've had tip guides that wore much faster than I would have
thought reasonable. One was a rod I'd built myself and the other was one I
had received for a product review. In both cases I opted to replace the tip
myself. Either the old-fashioned melting cements (like Pflueger Bulldog) or
epoxy can be softened with a little heat and the tip easily pulled off.
Just be careful not to use excessive heat which may damage the epoxy resin
in the rod itself. I usually use a loop of string (to avoid burning my
fingers) through the tip guide, and pass the barrel of the tip guide back
and forth quickly over an alcohol lamp while pulling gently on the loop. As
soon as the cement (or epoxy) softens, the tip guide will slide off.